A history of Infusoria : including the Dismidiaceoe and Diatomaceoe, British and foreign / by Andrew Pritchard.
- Date:
- 1861
Licence: Public Domain Mark
Credit: A history of Infusoria : including the Dismidiaceoe and Diatomaceoe, British and foreign / by Andrew Pritchard. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![and to assimilate thoir organization Avith that ho attributed to other Polj'- gastrica, represented the larger oil-vesicles and starch-grains to be either stomach-sacs or ova,—at one time the one, at another the otlier, in a purely arbitrary fashion. Some again of the more transparent or rcfi-acting vesicles were, Avith no shadow of reason, called fecundating or spei-matic glands. An attempt to show the error of such an hypothesis of internal organization would be futile and imcalled for at the present day. Habitats, Disteibution, Appeahance in Masses, and Vital Endowments OF DESMIDIEiE. VEGETABLE NaTUKE AND AFFINITIES. MoDE OF COLLECTION. Tlie Desmidieaj live in fresh water, in ditches and ponds, and rarely in streams, except when these are very sluggish. They will often rapidly appear in a recent collection of water, and are not destroyed when the pool is chied up, as their reappearance immediately after a shower proves; nevertheless, ponds which do not dry up during the summer, and pools in boggy gi-oimd, are richer in these organisms, provided the water remains sweet. To quote Mr. Ealfs's experience— The Desmidiese prefer an open coimtry. They abound on moors and in exposed places, but are rarely found in shady woods or in deep ditches. To search for them in turbid water is useless; such situations ai'e the haunts of animals, not the habitats of the Desmidiefe, and the waters in wliich the latter are present are always clear to the veiy bottom. They no doubt inhabit the fresh waters in all parts of the globe, for they have been found wherever sought in each hemisphere. StiU the sevei-al genera and species are not universal, for, as in the case of higher plants, some species are ijeculiar to one country, others to another; and in the same countiy the presence and prevalence of any one species will be determined by the physical featiu'es of localities, by the nature of the soU, and the Hke. The distribution, however, of the Desmidieae has not been inquired into so fully as to justify any attempt to lay down special laws. Oftentimes in small collections of water, Desmidieae of the same or of vaiious species and genera multiply to such an extent as to colour the water, and in the case of the filamentous species, to appear in filmy masses on the surface or at the bottom of the pool; stUl this enormous multipKcation, and the coloration of the water they inhabit, are far less frequent in tlie case of the family in question than with others—for instance, the Euglcneae, or even the Diatomeae. Mrs. Thomas (op. cit. p. 36) has described the gi-een masses formed by Cosmanum, which during summer and autumn would float to the siu-faee, rapidly disengaging oxygen as the sun shone on them, and sinking again to the bottom -with the coolness of the evening. Later in the year, masses would adhere to the inner surface of the bottle in the form of a thin pellicle, or coUect in slimy masses, which appeared to dissolve with the wannth of the coming spring. The green colour changed to that of a reddish yeUow; and it might have been thought that all was dead, did not the microscope show the same beautiful green, both in young and full-grown plants, together with much bright red and brown, apparently the casings of the sporangia Large Cosmaria stiU in active motion (the remains of the mature growtli of the pre- ceding summer) lay imbedded in the mass, when a small portion was separated for microscopic observation, as well as clusters of young ones (I. 13, 14). When the bottle had remained more than a year untouched, except for change of water, these masses increased in Icatheiy hardness; green life was not extinct, but became feeble in colour, and too much changed to warrant further observations, whUe a small portion placed in another bottle, and more freely exposed to the light, multi])Iied Avith great rapidity. Many of the vital endoM-ments of the Desmidien! liave already been do-](https://iiif.wellcomecollection.org/image/b21910224_0036.jp2/full/800%2C/0/default.jpg)
