410 MICROSCOPIC FORMS OF ANIMAL LIFE. 



Amoeba ingests and digests both Vegetable and Animal food, 

 and applies it to the nutrition of its body, no less effectively than 

 an Animal possessing the most complex digestive and circulating 

 apparatus. And in the present state of our knowledge, we seem 

 justified in laying it down as the most ready and certain dif- 

 ferential character we are acquainted with, between the most 

 closely related Protophyta and Protozoa, that the former (with 

 the exception of the Fungi) decompose carbonic acid under the 

 influence of light, and acquire a I'ed or green color from the new 

 compounds which they form in their interior ; whilst the latter, 

 having no such power,^ receive animal and vegetable organisms, 

 or particles of such, into the interior of their bodies, Avhere they 

 extract from them the ready prepared nutriment they are fitted 

 to yield. 



264. Rhizopoda. — The two creatures above described as the 

 types of the simplest form of Protozoic life, are not now regarded 

 as Infusory Animalcules, among which they were ranked by Prof. 

 Ehrenberg ; but are considered as the types of a distinct subdi- 

 vision, to which the name of Rhizopoda has been assigned by M. 

 Dujardin ; this name very appropriately representing the leading 

 feature in their organization, which consists in the extension of 

 their sarcode-body into long root-like processes, whereby their 

 aliment is drawn into its substance. In by far the larger propor- 

 tion of the animals included in this group, a carapace or shell is 

 formed, either by the consolidation of the superficial layer of the 

 sarcode-body through impregnation of its substance with mineral 

 matter, or (as appears to be the case in some instances) by the 

 agglutination of particles of sand, &c., with a viscid secretion 

 exuded from its surface. This " cai-apace," in Arcella (Fig. 193, 

 c, d), has for its basis a layer of dense membrane, which seems 

 analogous to the firm envelope of the Desmidiaccfe (§ 164), and 

 to that which constitutes the basis of the " lorica" of Diatomacese 

 (§ 172) ; and in some species it sends out spinous prolongations 

 like those of the former; whilst in others its surface exhibits 

 symmetrical markings that resemble those of the latter. Its ma- 

 terial diflfers, however, from that of the cellulose wall of Vegetable 

 cells, as may be shown by the efl:ects of reagents ; and seems to 

 be rather a modification of homy matter, probably resembling 

 the chitine which gives solidity to the integuments of Insects. 

 ISTot unfrequently it contains particles of sand, minute Diatoms, 

 &c., imbedded in its substance. The DIfflugia (Fig. 193, A, b) 

 differs in no essential particular from Arcella, save in the form 

 of its carapace, which is pitcher-shaped, instead of being shield- 

 like or dish-shaped. In the one case, as in the other, the cara- 

 pace has but a narrow opening, through which alone can the 

 " pseudopodia" be projected. The general nature of these ani- 



' Many instances have been cited, of Animalcules acquiring a green color by the de- 

 composition of carbonic acid under the influence of hght; but there can be no doubt in 

 the mind of any one who is familiar with the results of recent microscopic research, 

 that in all these cases, the supposed Animalcules were really Protnphytes. 



