Motile N'uble x6.
The male gametophyte is represented by one or few cells and, except in a few primitive forms where the male cell still retains the motile character as in the Pteridophyta, is carried passively to the macrospore in a development of the pollen grain, the pollen tube.
In GY~~1NospERMsso-called because the ovules (and seeds) are borne on an open sporophyll or carpelthe microsporophylls and macrosporophylls are not as a rule associated in the same shoot and are generally arranged in cone-like structures; one or two small prothallial cells are formed in the germination of the microspore; the male cells are in some older members of the group motile though usually passive.
In some cases both the nucleus and the chromatophores may be carried along in the rotating stream, but in others, such as T.Titeila, the chloroplasts may remain motionless iii a non-motile layer of the cytoplasm in direct contact with the cell wall.i Desmids, Diatoms and Oscillaria show creeping movements probably due to the secretion of slime by the cells; the swarmspores and plasmodium of the Myxomycetes exhibit amoehoid movements; and the motile spores of Fungi and Algae, the spermatozoids of mosses, ferns, &c., move by means of delicate prolongations, cilia or flagella cf the protoplast.
May be motile (some Al- - -
Gae) or non-motile, as in Spirogyra, Mucor, Bas- -
Cent; the male cell may be motile or non-motile.
In the Florideae, Lichens and Laboulbenjaceae the, male cell is a non-motile spermatium, which is carried to the female organ.
In Monoblepliaris, one of the lower Fungi, in some Algae, in the Vascular Cryptograms, in Cycads (Zamia and Cycas), and in Ginkgo, an isolated genus of Gymnosperms, the male cell is a motile spermatozoid with two or more cilia.
Cell, which is non-motile, is carried to the oosphere by means of a pollen tube.
Many motile unicellular Algae and swarm spores is also probably concerned with the active response to light exhibited by these organisms. In Euglena viridis, which has been most carefully studied in this respect, the flagellum which brings about the movement bears near its base a minute spherical or oval refractive granule or swelling which is located just in the hollow of the red pigment-spot (fig.
II.) - cells that are motile and extremely phagocytic to these bacteria.
In the first stage the ammonium compounds are oxidized to nitrites by the agency of very minute motile bacteria belonging to the genus Nitrosomonas.
In two families motile articulated rods occur; in Triarthridae they probably simply expand the dimensions of the body in adaptation to life at the surface; or as a protection against being swallowed by their smaller foes.
Ploimoidaceae; subconical; corona bilobed; retractile foot absent or ciliated; motile appendages present in two families.
Nevertheless, the general appearance and structure of these motile forms so greatly resemble that of a Herpetomonad, or of the " pseudo-Herpetomonadine " forms of a Trypanosome which are obtained in cultures, that it cannot be doubted that the " Leishman-Donovan-Wright " bodies are closely connected with the Haemoflagellates.
Whether a spore results from the sexual union of two similar gametes (zygospore) or from the fertilization of an egg-cell by the protoplasm of a male organ (oospore); or is developed asexually as a motile (zoospore) or a quiescent body cut off from a hypha (conidium) or developed along its course (oidium or chlamydospore), or in its protoplasm (endospore), are matters of importance which have their uses in the classification and terminology of spores, though in many respects they are largely of academic interest.
Motile zoospores which escape from the zoosporangium are present except in Aplanes.
The male organ (antheridium) consists of a few cells, the terminal one of which either abstricts from its end, or emits from its interior the non-motile spermatia, reminding us of those of the Florideae.
Thus, although isogamy consists in typical cases of a union of naked motile gametes by a fusion which begins at the beaked ends, and results in the formation of an immotile spherical zygote surrounded by a cell-wall, in Leptosira it is noticeable that the fusion begins at the blunt end; in a species of Chlamydomonas the two gametes are each included in a cell-wall before fusion; and in many cases the zygote retains for some time its motility with the double number of cilia.
The discovery by Brebner of the specific identity of Haplospora globosa and Scaphospora speciosa marks an important step in the advance of our knowledge of the group. Three kinds of reproductive organs are known: first, sporangia, which each give rise to a single tetra-, or multi-nucleate non-motile, probably asexual spore; second, plurilocular sporangia, which are probably antheridia, generating antherozoids; and third, sporangia, which are probably oogonia, giving rise to single uninucleate non-motile oospheres.
The Cryptomonadeae and Chromulineae are motile through the greater part of their life.
In Synura and Chromulina the cells form a spherical motile colony, recalling Volvocaceae.
Fertilization by means of non-motile spermatia and a trichogyne are known among the Fungi in the families Collemaceae and Laboulbeniaceae.
The experiment of Engelmann referred to deserves to be mentioned here, if only in illustration .of the use to which algae have been put in the study of physiological problems. Engelmann observed that certain bacteria were motile only in the presence of oxygen, and that they retained their motility in a microscopic preparation in the neighbourhood of an algal filament when they had come to rest elsewhere on account of the exhaustion of oxygen.
(From Strubell.) B, First motile larva.
Nor must we overlook the possibility that the endosporeformation in non-motile bacteria more than merely resembles the development of azygospores in the Conjugatae, and some Ulothricaceae, if reduced in size, would resemble them.
Independent movement is effected by special motile or- gans, the cilia or flagella.
R, J, K, L); and, finally, many actively motile forms have the cilia springing all round (Peritrichous), e.g.
A motile rodlet with one cilium and with a spore formed inside.
While many forms are fixed to the substratum, others are free, being in this condition either motile or immotile.
Motile rodlets (X 1000).
Division in all or any planes, colonies indefinite in shape and size, of cells in short chains, irregular clumps, pairs or isolated :- Micrococcus (Cohn), cells non-motile; Planococcus (Migula), cells motile.
Division planes regular and definite: - Sarcina (Goods.), cells non-motile; growth and division in three successive planes at right angles, resulting in packet-like groups; Planosarcina (Migula), as before, but motile; Pediococcus (Lindner), division planes at right angles in two successive planes, and cells in tablets of four or more; Streptococcus (Billr.), divisions in one plane only, resulting in chains of cells.
Sporogenous rodlets cylindric, not altered in shape: - Bacillus (Cohn), non-motile; Bactrinium (Fischer), motile, with one polar flagellum (monotrichous); Bactrillum (Fischer), motile, with a terminal tuft of cilia (lophotrichous); Bactridium (Fischer), motile, with cilia all over the surface (peritrichous) .
Sporogenous rodlets, spindle-shaped: - Clostridium (Prazm.), motile (peritrichous).
Sporogenous rodlets, drumstick-shaped: - Plectridium (Fischer), motile (peritrichous).
Divisions perpendicular to the long axis: - Vibrio (Muller-Ldffler), commashaped, motile, monotrichous; Spirillum (Ehrenb.), more strongly curved in open spirals, motile, lopho trichous; Spirochaete (Ehrenb.), spirally coiled in numerous close turns, motile, but apparently owing to flexile movements, as no cilia are found.
(a) Filaments rigid, non-motile, sheathed: - Crenothrix (Cohn), filaments unbranched and devoid of sulphur particles; Thiothrix (Winogr.), as before, but with sulphur particles; Cladothrix (Cohn), filaments branched in a pseudo-dichatomous manner.
The principal objections to this system are the following: - (1) The extraordinary difficulty in obtaining satisfactory preparations showing the cilia, and the discovery that these motile organs are not formed on all substrata, or are only developed during short periods of activity while the organism is young and vigorous, render this character almost nugatory.
Subtilis pass in a few hours after commencement of growth from a motile stage with peritrichous cilia, into one of filamentous growth preceded by casting of the cilia.
(3) The monotrichous and lophotrichous conditions are by no means constant even in the motile stage; thus Pseudomonas rosea (Mig.) may have I, 2 or 3 cilia at either end, and would be distributed by Fischer's classification between Bactrinium and Bactrillum, according to which state was observed.
In ordinary arable soil there exist motile rod-like bacteria, Bacterium radicicola.
By this is meant the aggregation into clumps of the bacteria uniformly distributed (natiai n an indifferent fluid; if the bacterium is motile its movement is arrested during the process.
By sensitiveness to chemical substances in their surroundings - a property which is not peculiar to them but is possessed by various unicellular organisms, including motile bacteria.
Microspore spherical or oval, with or without a bladder-like extension of the exine, containing a prothallus of two or more cells, one of which produces two non-motile or motile male cells.
One of the most important discoveries made during the latter part of the 19th century was that by Ikeno, a Japanese botanist, who first demonstrated the existence of motile male cells in the genus Cycas.
The discovery by the Japanese botanist 'Erase of the development of ciliated spermatozoids in the pollen-tube of Ginkgo, in place of the non-motile male cells of typical conifers, served as a cogent argument in favour of separating the genus from the Coniferales and placing it in a class of its own.
The latter ultimately divides in the apex of the pollen-tube into two non-motile generative cells.
After the egg-cells have been fertilized by the non-motile male cells they grow into tubular proembryos, producing terminal embryos.