- Diagram of morphological rela veloped mouth, gut and tions of Rotifera.
The standing of the Trichoptera in a position almost ancestral to the Lepidoptera is one of the assured results of recent morphological study, the mobile mandibulate pupa and the imperfectly suctorial maxillae of the Trichoptera reappearing in the lowest families of the Lepidoptera.
Considering the wide differences between the two groups in the size and external characters, and in the mode of life, including the mode of feeding, it is indeed surprising that in every important organ the two groups should show a fundamental morphological identity.
This has had a most important effect on the development in recent years of morphological anatomy.
The explicit adoption of this point of view has had the effect of clearing up and rendering definite the older morphological doctrines, which for the most part had no fixed criterion by which they could be tested.
B~it the staining reactions of nuclei may vary at different stages of their development; and it i~ probable that there is no method of staining which differentiates with certainty the various morphological constituents of the nucleus.
The small forms known as Schizomus and Hubbardia are of special interest from a morphological point of view.
- With regard to the vexed questions of the morphological nature and of the affinities of the Cestodes, divergent views are still held.
Divergent views have been held as to the morphological significance of the pneumatophore.
Rosenkranz, who in his work Hegel's Naturphilosophie seeks to develop Hegel's idea of an earthorganism in the light of modern science, recognizing in crystallization the morphological element.
Evolution, or development, is, in fact, at present employed in biology as a general name for the history of the steps by which any living being has acquired the morphological and the physiological characters which distinguish it.
morphological identity) between the differentiated tissues of an Anthocerotean sporogonium and those of the sporophyte in the higher plants.
This is a morphological term given to the particular~ type of hydrom found in both Pteridophytes and Phanerogams, together with the parenchyma or stereom, or both, included within the boundaries of the hydrom tissue strand.
Theoretically this branch of the subject should connect with and form the completion of morphological anatomy, but the field, has not yet been sufficiently explored to allow of the necessary synthesis.
The pursuit of this study has not only thrown valuable light on the economy of the plant as a whole, but forms an indispensable condition of the advance of morphological anatomy.
Notwithstanding the fact, however, that these cells are capable of acting as very efficient lenses the explanation given by Haberlandt has not been widely accepted and evidence both morphological and physiological has been brought forward against it.
At the present time some objection is being taken to this purely morphological conception of the body and its parts as being too abstract.
When two organs can be traced along the same line of descent to one primitive form, that is when they are found to be mono phyletic, their homology is complete; when, however, they are traceable to two primitive forms, though these forms belong to the same morphological series, they are polyphyletic and therefore only incompletely homologous.
All organs performing the same function and showing similar adaptations are said to be analogous or homoplastic, whatever their morphological nature may be; hence organs are sometimes both homologous and analogous, sometimes only analogous.
In this, as in all morphological inquiries, two lines of investigation have to be followed, the phylogenetic and the ontogenetic. Beginning with its phylogeny, it appears, so far as present knowledge goes, that the differentiation of the shoot of the sporophyte into stem and leaf first occurred in the Pteridophyta; and, in accordance with the views of Bower (Origin of a Land..
These changes may be brought about by external causes, such as the attacks of insects or of fungi, alterations in external conditions, &c., or by some unexplained internal disturbance of the morphological equilibrium.
Useful and suggestive as they often are, teratological facts played, at one time, too large a part in the framing of morphological theories; for it was thought that the monstrous form gave a clue to the essential nature of the organ assuming it.
there is morphological differentiation, which can be traced in the distinction of the members of the body, root, stem, leaf, &c.; there is physiological differentiation, which can be traced in the adaptation of these members to various functions.
AdaptationThe morphological and physiological differentiation of the plant-body has, so far, been attributed to (I) the nature of the organism, that is to its inherent tendency towards higher organization, and (2) to the indefinite results of the external conditions acting as a stimulus which excites the organism to variation, but does not direct the course of variation.
Moreover, had the evolution of plants proceeded along the line of adaptation, the vegetable kingdom could not be subdivided, as it is, into the morphological groups Thallophyta, Bryophyta, Pteridophyta, Phanerogamia, but only into physiological groups, Xerophyta, Hygrophyta, Tropophyta, &c.
Sachs was the first to formulate the theory that morphological differences are the expression of differences in material composition.
Full morphological and organographical details are given in the articles on the various groups of plants, such as those on the Algae, Bryophyta, Pteridophyta, Angiosperms, Gymnosperms, &c. The following works may also be consulted:
The two conceptions which may now be said to animate the theory of geography are the genetic, which depends upon processes of origin, and the morphological, which depends on facts of form and distribution.
It is to be noted that often no absolute line of demarcation can be drawn in regard to these regions, their definitions being rather convenient than morphological.
The results are as interesting from a morphological point of view (showing the subtle and gradual modifications of these organs in their various adaptations), as they are sparse in taxonomic value, far less satisfactory than are those of the hind-limb.
Goodrich, endorsed by Lankester, led to the opinion that under the general morphological conception of "nephridium" were included two distinct sets of organs, viz.
It is possible, however, that those oviducts belong to a separate morphological category, more comparable to the dorsal pores and to abdominal pores in some fishes.
In the Eudrilidae there are spermathecae of different morphological value.
The vascular system does not readily lend itself to morphological comparison between such widely different animals as Balanoglossus and Amphioxus, and the reader is therefore referred to the memoirs cited at the end of this article for further details.
(From Lankester, "Limulus an Arachnid.) of adaptation to the changed physiological conditions of respiration, and not of morphological significance, since a pair of renal excretory tubes of this nature is found in certain Amphipod Crustacea (Talorchestia, &c.) which have abandoned a purely aquatic life.
L.) compared is difficult when we introduce, as seems inevitable, the question of efficiency and power, and do not confine the question to the perfection of morphological development.
Between the two and at the highest point of the arc, so far as morphological differentiation is concerned, stands the scorpion; near to it in the trilobite's direction (that is, on the ascending side) are Limulus and the Eurypterines - with a long gap, due to obliteration of the record, separating them from the trilobite.
Cuvier's doctrine of four plans of structure was essentially a morphological one, and so was the single-scale doctrine of Buffon and Lamarck, to which it was opposed.
Cuvier's morphological doctikne received its fullest development in the principle of the " correlation of parts," which he applied to palaeontological investigation, namely, that every animal is a definite whole, and that no part can be varied without entailing correlated and law-abiding variations in other parts, so that from a fragment it should be possible, had we a full knowledge of the laws of animal structure or morphology, to reconstruct the whole.
Owen not only occupied himself with the dissection of rare animals, such as the Pearly Nautilus, Lingula, Limulus, Protopterus, Apteryx, &c., and with the description and reconstruction of extinct reptiles, birds and mammals - following the Cuvierian tradition - but gave precision and currency to the morphological doctrines which had taken their rise in the beginning of the century by the introduction of two terms, " homology " and " analogy," which were defined so as to express two different kinds of agreement in animal structures, which, owing to the want of such " counters of thought," had been hitherto continually confused.
The wave of morphological speculation, with its outcome of new systems and new theories of classification.
His true greatness can only be estimated by a consideration of the fact that he was a great teacher not only of human and comparative anatomy and zoology but also of physiology, and that nearly all the most distinguished German zoologists and physiologists of the period 1850 to 1870 were his pupils and acknowledged his leadership. The most striking feature about Johann Miller's work, apart from the comprehensiveness of his point of view, in which he added to the anatomical and morphological ideas of Cuvier a consideration of physiology, embryology and microscopic structure, was the extraordinary accuracy, facility and completeness of his recorded observations.
In arranging plants according to a natural method, we require to have a thorough knowledge of structural and morphological botany, and hence we find that the advances made in these departments have materially aided the efforts of systematic botanists.
This gives rise to the great morphological difference, that in the former regions, the Astin-tagh and the Kuruk-tagh, the products of disintegration are almost always carried away by the wind, and so disappear; no matter how powerful or how active the disintegration may be, none of the loosened material ever succeeds either in gathering amongst the mountains or in accumulating at their foot.
But though the great morphological features of this latitudinal valley forcibly recall the latitudinal valleys of Tibet, the climatic differences give rise to differences between the basins corresponding to the differences between the mountain-ranges themselves.
In external form and appearance the Hydrozoa exhibit such striking differences that there would seem at first sight to be little in common between the more divergent members of the group. Nevertheless there is no other class in the animal kingdom with better marked characteristics, or with more uniform morphological peculiarities underlying the utmost diversity of superficial characters.
The sense-organs are always situated at the margin of the unbrella and may be distinguished from the morphological point of view into two categories, according as they are, or are not, derived from modifications of tentacles; in the former case they are termed tentaculocysts.
- Representative Mammalian, Avian and Reptilian Trypanosomes, to illustrate the chief morphological characters.
(b) He contends that, when matter ascends to the evolution of organic life, the unconscious has a power, over and above its atomic volitions, of introducing a new element, and that in consequence the facts of variation, selection and inheritance, pointed out by Darwin, are merely means which the unconscious uses for its own ends in morphological development.
Under the vague term " double " many very different morphological changes are included.
This is apparently owing to the facts that too much has been attempted in the definition, and that differences arise according as we aim at a morphological or a physiological definition.
On this basis, with other interesting morphological comparisons, Brefeld erected his hypothesis, now untenable, that the Ascomycetes and Basidiomycetes diverge from the Zygomycetes, the former having particularly specialized the ascus (sporangial) mode of reproduction, the latter having specialized the conidial (indehiscent one-spored sporangiole) mode.
Brefeld regarded the promycelium as a kind of basidium, bearing lateral or terminal conidia (comparable to basidiospores), but since the number of basidiospores is not fixed, and the basidium has not yet assumed very definite morphological characters, Brefeld termed the group Hemibasidii, and regarded them as a halfway stage in the evolution of the true Basidiomycetes from Ph co Y Y mycetes, the Tilletia type leading to the true basidium (Autobasidium), the Ustilago type to the proto pm basidium, with lateral spores; but this p m view is based on very poor evidence, so that it is best to place these forms?p, c;,::, as a separate group, the Ustilaginales.
In the last-named family the single morphological species Erysiphe graminis is found growing on the cereals, barley, oat, wheat, rye and a number of wild grasses (such as Poa, Bromus, Dactylis).
The vast advance in knowledge of the existing forms of living things that has been acquired and recorded since 1859 has accentuated the difficulty of finding any morphological criteria for species.
Investigation has shown that many other parts of a plant which externally appear very different from ordinary leaves are, in their essential particulars, very similar to them, and are in fact their morphological equivalents.
All modifications of leaves follow the same laws of arrangement as true leaves - a fact which is of importance in a morphological point of view.
Parker observes of their brain capacity and is an additional testimony to their low morphological rank.
But the great diversity of these abnormal cases as shown in the examples cited above suggests the use of great caution in formulating definite morphological theories upon them.
The similarity of the morphological characters of one group of fungi to those of certain algae has earned for it the name of Phycomycetes or alga -fungi.
Notwithstanding the absence of chlorophyll, and the consequent parasitic or saprophytic habit, Bacteriaceae agree in so many morphological features with Cyanophyceae that the affinity can hardly be doubted.
standing their acknowledged morphological affinity with Cyanophyceae, or, in recognition of the incongruity of effecting such a separation, the whole group of the Schizophyta - that is to say, the Cyanophyceae in the narrow sense, together with Bacteriaceae, is included or excluded together.
Altogether it is difficult on morphological grounds to resist the conclusion that Florideae present the same fundamental phenomenon of alternation of generations as prevails in the higher plants.
The presence of phycocyanin, phyco a role in the morphological development of land plants is entirely wanting in algae, such conducting tissues as do exist in the larger Phaeophyceae and Rhodophyceae serving rather for the convection of elaborated organic substance, and being thus comparable with the phloem of the higher plants.
Thus Goethe had no great sympathy for the war of liberation which kindled young hearts from one end of Germany to the other; and when the national enthusiasm rose to its highest pitch he buried himself in those optical and morphological studies, which, with increasing years, occupied more and more of his time and interest.
The renal organs of the oyster were discovered by Hoek to agree in their morphological relations with those of other lamellibranchs.
Tubers are also sometimes formed on aerial branches, as in some Aroids, Begonias, &c. The production of small green tubers on the haulm, in the axils of the leaves of the potato, is not very unfrequent, and affords an interesting proof of the true morphological nature of the underground shoots and tubers.
Even when used in conjunction with purely morphological characters, these physiological properties are too variable to aid us in the discrimination of species and genera, and are apt to break down at critical periods.
Although much progress has been made in determining the value and constancy of morphological characters, we are still in need of a sufficiently comprehensive and easily applied scheme of classification, partly owing to the existence in the literature of imperfectly described forms, the life-history of which is not yet known, or the microscopic characters of which have not been examined with sufficient accuracy and thoroughness.
The principal attempts at morphological classifications recently brought forward are those of de Toni and Trevisan (1889), Fischer (1897) and Migula (1897).
I) led him to propose a scheme of classification based on these and other morphological characters, and differing essentially from any preceding one.
The work of numerous observers has shown that the free nitrogen of the atmosphere is brought into combination in the soil in the nodules filled with bacteria on the roots of Leguminosae, and since these nodules are the morphological expression of a symbiosis between the higher plant and the bacteria, there is evidently here a case similar to the last.
The application of the morphological method to the Crustacea may perhaps be dated from the work of J.
Its morphological nature, however, is clearly shown by its development.
somite corresponding to the eyes (the morphological nature of which is discussed below), the smallest number of head-somites so united in any Crustacean is five.
Even where a large number of the somites have fused, there is generally a marked change in the character of the appendages after the fifth pair, and since the integumental fold which forms the carapace seems to originate from this point, it is usual to take the fifth somite as the morphological limit of the cephalon throughout the class.
The morphological nature of this system is unknown.
Although the excretory function of these has been demonstrated by physiological methods, however, their morphological relations are not clear.
This coronet forms the most conspicuous and beautiful part of the flower of many species, and consists of outgrowths from the tube formed subsequently to the other parts, and having little morphological significance, but being physiologically useful in favouring the cross-fertilization of the flower by means of insects.
Among existing Cycadophyta we find surviving types which, in their present isolation, their close resemblance to fossil forms, and in certain morphological features, constitute links with the past that not only connect the present with former periods in the earth's history, but serve as sign-posts pointing the way back along one of the many lines which evolution has followed.
Although there are several morphological features in the three genera of Gnetales which might seem to bring them into line with the Angiosperms, it is usual to regard these resemblances as parallel developments along distinct lines rather than to interpret them as evidence of direct relationship.
It is difficult to estimate the value of abnormalities as evidence bearing on morphological interpretation; the chief danger lies perhaps in attaching undue weight to them, but there is also a risk of minimizing their importance.
Broadly speaking, these families make their first appearance in time in the order given above, and show a progressive morphological evolution along certain special lines.
Brief reference may also be made to the morphological importance of extraordinary length or shortness in the skulls of mammals - dolichocephalism and brachycephalism; both these features being apparently characteristic of specialized types, the former condition being (as in the horse) often, although not invariably, connected with length of limb and neck, and adaptation to speed, while brachycephalism may be correlated with short limbs and an abbreviated neck.
In structure they resemble the roots, but their morphological nature is uncertain.
The upright stems were attached to the soil by a number of dichotomously branched members (Stigmaria), which, whatever their morphological nature may be, appear to have performed the function of roots: they bore numerous cylindrical appendages, which penetrated the soil on all sides.
Protopodite, endopodite, exopodite, and epipodite were considered to be the morphological units of the crustacean limb.
Since the proboscis is a purely larval organ in this genus, it may be supposed that the coelomic space which properly belongs to it fails to develop, but that the praeoral hood itself is none the less the morphological representative of the proboscis.
The Annelidan affinities are superficially indicated in so marked a manner by the thinness of the cuticle, the dermomuscular body-wall, the hollow appendages, that, as already stated, many of the earlier zoologists who examined Peripatus placed it among the segmented worms; and the discovery that there is some solid morphological basis for this determination constitutes one of the most interesting points of the recent work on the genus.
Mic. Sci., 1885-1888); Studies from the Morphological Lab.
of the Studies from the Morphological Lab.
This fact strongly confirms the conclusion, drawn from morphological and anatomical characters, that the Botryopterideae were true Ferns.
This review incorporates new data on morphological diversity in galls from several large assemblages of Cretaceous and early Tertiary angiosperm leaves.
New diagnostic morphological criteria have been found, and these are used routinely to rapidly confirm the identify the bean anthracnose isolates.
Molecular characters have been used in conjunction with morphological characters to understand patterns of evolution within the genus arum.
Be aware of, and to recognize, the main morphological and compositional features which allow assignation of an individual fossil to each group.
Brain, spleen, marrow and peripheral blood morphological research was also carried out under the same conditions of animal RF EMF irradiation.
When a cell undergoes apoptosis, they have distinct morphological characteristics.
The dictionary performs syntax analysis of phrases and determines morphological composition of each given word for English-language entries.
Knowledge of morphological theory and/or dialectology will be an advantage, although specific training will be provided.
epithelial dysplasia as a morphological manifestation of gastric precancer can serve a marker of the risk of malignant transformation.
Developmental genetics, particularly the generation of morphological diversity.
Even one researcher said " At the morphological level feathers are traditionally considered homologous with reptilian scales.
You must know a fair amount about Greek dialects and morphological rules to retrieve the differently inflected occurrences of a " word.
Each line in the resource file shows an inflected form, its part of speech, its related lemma and its morphological information.
Free or bound lexemes are most natural as morphological bases (e.g.
Sixty six morphological character matrices were analyzed using parsimony.
Both males and hermaphrodite seam cell lineages are affected although the hermaphrodites do not exhibit any obvious gross morphological phenotype.
After some introductory remarks, the chapters cover phonology, morphological processes, morphosyntax, and syntax.
The first three morphological segments to appear are thoracic segments.
It is argued that phonological or phonetic similarity of forms favors diachronic syncretism in certain morphological contexts.
syntagmatic context for indexical purposes are morphological metaphors (e.g.
Morphological alterations in mouse testis by a single dose of malathion.
tetraploid species, using 29 morphological characters was carried out using different outgroups.
yeasts was by studying morphological differences with the aid of the microscope.
of our knowledge of the structure and course of the vascular strands of the higher plants (IJeber den Bau und die Anordnung der Gefssbundel bei den Stamm und Wurzel der Phanerogamen, Beitrage zur wissenschaftlichen Botanik, Heft i., Leipzig, 1859); to the second the establishment of the sound morphological doctrine of the central cylinder of the axis as the starting-point for the consideration of the general arrangement of the tissues, and the first clear distinction between primary and secondary tissues (Botanische Zeitung, 186I and 1863); to the last the putting together of the facts of plant anatomy known up to the middle of the eighth decade of the century in that great encyclopaedia of plant anatomy, the Vergleichende Anatomie der Vegetationsor gene bei den Phanerogamen und Farnen (Stuttgart, 1876; Eng.
While convincing us that the plants of past ages in the earths history were exposed to very similar conditions of life, and made very much the same adaptive responses as their modern representatives, one of the main results of this line of work has been to reveal important data enabling us to fill various gaps in our morphological knowledge and to obtain a more complete picture of the evolution of tissues in the vascular plants.
Thirdly, we have to record very considerable progress in our knowledge of distinctively morphological anatomy, i.e.
Since about 1895 this branch has been most actively pursued in England, where the work of Boodle and of Gwynne-Vaughan especially on Ferns) has been the most important, leading to a coherent theory of the evolution of the vascular system in these plants (Tansley, Evolution of the Filicinean Vascular System, Cambridge, 1908); and in America, where Jeffrey has published important papers on the morphology of the vascular tissues of the various groups of Pteridophytes and Phanerogams and has sought to express his conclusions in a general morphological theory with appropriate terminology.
Physiological and Morphological Di,fferentiation.The first indication of this differentiation in the vegetative body of the plant can be seen not only in the terrestrial green plants which have been particularly referred to, but also in the bulkier seaweeds.
But admitting the validity of this criticism, and even going so far as to question the possibility of ever devising absolutely inclusive and, at the same time, exclusive definitions, no sufficient reason is adduced for giving up all attempt at morphological analysis.
Homology.All members belonging to the same morphological category are said to be homologous, however diverse their functions.
Taking first the conversion of members of one morphological category into those of another, this has been actually observed, though rarely.
This view he subsequently modified to thisthat a relatively small proportion of diverse substance in each of these parts would suffice to account for their morphological differences.
If this be so,it may justifiably be inferred that both normal and abnormal morphological features may be due to the presence of enzymatic substances secreted by the protoplasm that determine the course of development.
From the morphological point of view it is more important to distinguish the associations of forms, such as the mountain mass or group of mountains radiating from a centre, with the valleys furrowing their flanks spreading towards every direction; the mountain chain or line of heights, forming a long narrow ridge or series of ridges separated by parallel valleys; the dissected plateau or highland, divided into mountains of circumdenudation by a system of deeply-cut valleys; and the isolated peak, usually a volcanic cone or a hard rock mass left projecting after the softer strata which embedded it have been worn away (Monadnock of Professor Davis).
Classification Of Birds Fiirbringer's great work, published in the year 1888 by the Natura Artis Magistra Society of Amsterdam, enabled Gadow not only to continue for the next five years the same lines of morphological research, but also further to investigate those questions which were still left in abeyance or seemed to require renewed study.
The ordinary mycelium is the gametophyte since it hears the ascogonia and aritheridia when present; the cqe Two questions of great theoretical importance have been raised over and over again in connexion with yeasts, namely, (I) the morphological one as to whether yeasts are merely degraded forms of higher fungi, as would seem implied by their tendency to form elongated, hypha-like cells in the veils, and their development of "ascospores" as well as by the wide occurrence of yeast-like "sprouting forms" in other fungi (e.g.
A few examples are appended: Some of the Uredineae also exhibit the peculiarity of the development of biologic forms within a single morphological species, sometimes termed specialization of parasitism; this will be dealt with later under the section Physiology.
Complex words that typically recur to the syntagmatic context for indexical purposes are morphological metaphors (e.g.
A morphological character matrix was compiled for the fifteen terminal taxa.
Analysis of species relationships omitting the four known tetraploid species, using 29 morphological characters was carried out using different outgroups.
Thus, the diagnosis may be determined during history taking or if it is the fetus, during the morphological ultrasound at 16-19 weeks gestation.
Since, however, medusa-colonies occur only in one group, the Siphonophora, and divergent views are held with regard to the morphological interpretation of the members of a siphonophore, only the first three of the above sub-divisions of hydromedusa morphology will be dealt with here in a general way, and the morphology of the Siphonophora will be considered under the heading of the group itself.
The special property of the medusa is the umbrella, distinguishing the medusa at once from other morphological types among the Coelentera.
The Hertwigs when they discovered the endoderm-lamella showed on morphological grounds that polyp and medusa are independent types, each produced by modification in different directions of a more primitive type represented in development by the actinulastage.
The general theories of Siphonophoran morphology are discussed below, but in enumerating the various types of appendages it is convenient to discuss their morphological interpretation, at the same time.
Many views have been put forward as to the morphological relationship between the two types of person in the Hydromedusae.
Erasmus Darwin (Zoonomia, 17 94), though a zealous evolutionist, can hardly be said to have made any real advance on his predecessors; and, notwithstanding the fact that Goethe had the advantage of a wide knowledge of morphological facts, and a true insight into their signification, while he threw all the power of a great poet into the expression of his conceptions, it may be questioned whether he supplied the doctrine of evolution with a firmer scientific basis than it already possessed.
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.