32 INFUSORIA. 



the more refined characteristics now adopted in zoological classifi- 

 cation, Crustaceans and Insects, as well as the larvae of Annelidans, 

 Zoophytes, and Echinoderms, have been successively withdrawn from 

 the group and located in their appropriate stations, while innumerable 

 zoospores and embryonic plants, together with the DesmidiaceaB and 

 the Diatomacese generally, are by common consent conceded to the 

 botanical series of Creation*. Still, as it would appear, the zoologist is 

 reluctant to dissever forms of life which habit has accustomed the micro- 

 scopical observer to associate with each other ; and even M. Dujardin, one 

 of the latest and most unprejudiced writers upon the history of these 



* It is by no means an easy task to indicate the boundary -line which separates 

 the animal from the vegetable kingdom. The most important difference, that the 

 vegetable cell^membrane contains no azote, while the animal cell-membrane does, 

 cannot be applied in doubtful cases, the tenuity of the membrane not allowing of the 

 investigation. That animals possess the power of locomotion, but plants not, is 

 incorrect as applied generally, and is still less applicable here, because many uni- 

 cellular Algse exhibit motion, frequently very energetic motion (when swarming), 

 whilst the ova of multicellular Alga are quiescent. The unicellular Algae differ 

 from the Infusoria in this, that their membrane and its appendages are not motile, 

 and that consequently they have a rigid form, whilst the latter in some instances 

 change their figure, and in others are furnished with motile cilia. The presence of 

 starch is, further, not invariably decisive as to the vegetable nature of a cell. The 

 ova of multicellular animals, the figure of which is rigid and unchangeable, may also 

 be recognized as not belonging to the unicellular Algse from their want of colour- 

 ing matter, which is present in the latter. 



We can scarcely expect Chemistry to decide what is animal and what plant. The 

 non-nitrogenous cellulose, which at first sight appears to be an exclusive attribute of 

 the vegetable, is also found pretty generally in the animal kingdom, as we learn 

 from the researches of G. Schmidt on Cynthia mammillaris, and those of Kolliker 

 and Lowig on a great number of the most various of the lower animals. Just as 

 little does chlorophyll appear to be exclusively characteristic of the vegetable world, 

 since the green granules and vesicles which occur imbedded in the parenchyma of 

 Hydra viridis, of various Turbellaria (Hypostomum mride and Tryphoplana viridata, 

 Schm.), and of Infusoria (Stentor polymorphus, Bursaria vernalis, Loxodes bursaria, 

 <Scc.), are probably closely allied to chlorophyll, if not identical with it. Erythro- 

 phyll also might be said to occur in the lower animals (for instance in Leucophrys 

 sanguinea and Astasia haematodes), in which latter the red colour frequently passes 

 into green, as does the erythrophyll of unicellular Algse 1 . 



1 The colouring matter of plants is distinguished by botanists into Chlorophyll, 

 Erythrophyll, Phycochrom, and Diatomin. The Chlorophyll is of a grass- or yellow- 

 green colour, little or not at all affected by diluted acids and alkalies, and frequently 

 turns brown upon the death of the plant. The Erythrophyll presents a red or pur- 

 ple colour, not changed by diluted acids, but becoming green on the addition of alka- 

 lies, and also most usually after death. The Phycochrom is verdigris-green or orange, 

 changed into orange by the action of diluted acid, and into a brown-yellow by that 

 of alkalies. The Diatomin is brownish yellow, not altered by diluted alkalies, but 

 changed into verdigris-green by diluted hydrochloric acid, and usually after death. 

 Vide Nageli, Gattungen einzelliger Algen, physiologisch und systematise!! bearbeitet : 

 Zurich, 1849. 



