They are now by many systematists united with the Acanthocephala and the Nematomorpha to form the group Nemathelminthes.
The study of the distribution of species dates back to the time of the early systematists, the study of vegetation to the time of the early botanical travellers.
The interesting little Rhodope veranyii, which has no odontophore, has been associated by systematists both with these simplified Opisthobranchs and with Rhabdocoel Planarians.
Yet as systematists their authors were no worse than Klein, whose Historiae Avium Prodromus, appearing at Lubeck in 1750, and Stemmata Avium at Leipzig in 1759, met with considerable favour in some quarters.
Be that as it may, he declares that characters drawn from the sternum or the pelvis - hitherto deemed to be, next to the bones of the head, the most important portions of the bird's framework - are scarcely worth more, from a classificatory point of view, than characters drawn from the bill or the legs; while pterylological considerations, together with many others to which some systematists had attached more or less importance, can only assist, and apparently must never be taken to control, the force of evidence furnished by this bone of all bones - the anterior palatal.
That the eggs laid by birds should offer to some extent characters of utility to systematists is only to be expected, when it is considered that those from the same nest generally bear an extraordinary family likeness to one another, and also that in certain groups the essential peculiarities of the egg-shell are constantly and distinctively characteristic. Thus no one who has ever examined the egg of a duck or of a tinamou would ever be in danger of not referring another tinamou's egg or another duck's, that he might see, to its proper family, and so on with many others.
Its basis is the classification of Cuvier, the modifications of which by Des Murs will seldom commend themselves to systematists whose opinion is generally deemed worth having.
The attempt of Des Murs was praiseworthy, but in effect it has utterly failed, notwithstanding the encomiums passed upon it by friendly critics (Rev. de Zoologie, 1860, pp. 176-183,313-325,370-373).2 Until about this time systematists, almost without exception, may be said to have been wandering with no definite purpose.
The pre-Darwinian systematists since the time of Von Baer had attached very great importance to embryological facts, holding that the stages in an animal's development were often more significant of its true affinities than its adult structure.
It is this introduction of the consideration of cell-structure and cell-development which, subsequently to the establishment of Darwinism, has most profoundly modified the views of systematists, and led in conjunction with the genealogical doctrine to the greatest activity in research - an activity which culminated in the work (1873-1882) of F.
The first post-Darwinian systematists naturally and without reflexion accepted of' the idea that existing simpler forms represent stages i n the gradual progress of development - are in fact survivors from past ages which have retained the exact grade of development which their ancestors had reached in past ages.
The length and armature of the pincers and the presence or absence of wings are perhaps the most important features used by systematists in distinguishing the various kinds.
A few systematists, among whom C. L.
Placed by most systematists in the family Scolopacidae, the birds commonly called Sandpipers seem to form three sections, which have been often regarded as Subfamilies - Totaninae, Tringinae and Phalaropodinae, the last indeed in some classifications taking the higher rank of a Family - Phalaropodidae.
The insects retained in the order Neuroptera as restricted by modern systematists are distinguished from the preceding orders by the presence of a resting pupal stage in the life-history, so that a " complete metamorphosis " is undergone.
The bulk of de Geer's " Dermaptera " form the order Orthoptera of modern systematists, which includes some Io,000 described species.
The Ibididae are more nearly related to the storks, Ciconiidae, and still more to the spoonbills, Plataleidae, with which latter many systematists consider them to form one group, the Hemiglottides of Nitzsch.
By recent systematists 5 genera and from 50 to 60 species of the family are recognized; but the characters of the former have never been satisfactorily defined, much less those of numerous subdivisions which it has pleased some writers to invent.
Indeed there are, or have been, systematists who would elevate the jays to the rank of a family Garrulidae - a proceeding which seems unnecessary.
Poulton, in an admirable discussion of contemporary views regarding species (presidential address to the Entomological Society of London 1904), has shown that Darwin did not believe in the objective existence of species, not only because he was led to discard the hypothesis of special creation as the explanation of the polymorphism of life, but because in practice as a working systematist he could neither find for himself nor ascertain from other systematists any settled criteria by which a group of specimens could be elevated into a genus, accepted as a species, or regarded as a variety.
The word "species" now signifies a grade or rank in classification assigned by systematists to an assemblage of organic forms which they judge to be more closely interrelated by common descent than they are related to forms judged to be outside the species, and of which the known individuals, if they differ amongst themselves, differ less markedly than they do from those outside the species, or, if differing markedly, are linked by intermediate forms. It is to be noted that the individuals may themselves be judged to fall into groups of minor rank, known as sub-species or local varieties, but such subordinate assemblages are elevated to specific rank, if they appear not to intergrade so as to form a linked.
In some external characters the lammergeyer is intermediate between the families Vulturidae and Falconidae, and the opinion of systematists has from time to time varied as to its proper position.
Seeds in which endosperm or perisperm or both exist are commonly called albuminous or endospermic, those in which neither is found are termed exalbuminous or exendospermic. These terms, extensively used by systematists, only refer, however, to the grosser features of the seed, and indicate the more or less evident.
It is equally clear that there is a broad analogy between the kind of characters on which systematists often have to rely for the separation of species and those which Mendelian workers have shown to behave in accordance with the Mendelian theories of mosaic inheritance with segregation.
We have still to admit with Darwin that it is difficult or impossible to assign utility to all the characters that distinguish species, and particularly to those characters by which systematists identify species.
On the other hand, the work of modern systematists shows an extraordinarily exact relation between their species and geographical locality, and the fact of divergent evolution can be almost demonstrated in museum collections when localities have been recorded exactly.
Little heed was paid to his opinion by most systematists, and when, more than half a century later, the axolotl was found to breed in its branchiferous condition, the question seemed to be settled once for all against him, and the genus Siredon, as it was called by J.
Mouette), for a group of sea-birds widely and commonly known, all belonging to the genus Larus of Linnaeus, which subsequent systematists have broken up in a very arbitrary and often absurd fashion.
The older group, however, even with such systematists as Ray (1703), Scheuchzer (1719), and Micheli (1729), embraced in addition the Cyperaceae 1 The word " grass " (0.
It is this second bract or flowering glume which has been generally called by systematists the " lower pale," and with the " upper pale " was formerly considered to form an outer floral envelope (" calyx," Jussieu; " perianthium," Brown).
In ordinary talk "Teal" seems to stand for any Ducklike bird of small size, and in that sense the word is often applied to the members of the genus Nettopus, though some systematists will have it that they are properly Geese.
The earthworms of England belong entirely to the three genera Lumbricus, Allolobophora and Allurus, which are further subdivided by some systematists; and these genera form the prevalent earthworm fauna of the Palaearctic region and are also very numerous in the Nearctic region.
For a long while their position was very much misunderstood, some systematists having placed them with the Alcidae or Auks, to which they bear only a relationship of analogy, as indeed had been perceived by a few ornithologists, who recognized in the penguins a very distinct order, I L.