224 THE MICROSCOPE AND ITS REVELATIONS. 



atmosphere or the water in which they live; and, like them, are distin- 

 guished by their power of decomposing Carbonic acid (CO 2 ) under the 

 influence of Light setting free its Oxygen, and combining its Carbon 

 with the elements of Water to form the Carbo-hydrogen compounds 

 (Starch, Cellulose, etc.), and with those of atmospheric Ammonia to 

 form Nitrogenous (albuminoid) compounds. And we shall find, more- 

 over, that even such Protozoa as have neither stomach nor mouth, 

 receive their alimentary matter direct into the very substance of their 

 bodies, in which it undergoes a kind of digestion; whilst ProtopJiyta 

 absorb through their external surface only, and take in no solid particles 

 of any description. With regard to motion, which was formerly consid- 

 ered the distinctive attribute of Animality, we now know not merely that 

 many Protophytes (perhaps all, at some period or other of their lives) 

 possess a power of spontaneous movement, but also that the instruments 

 of motion (when these can be discovered) are of the very same character 

 in the Plant as in the Animal; being little hair-like filaments, termed 

 cilia (from the Latin cilium, an eye-lash), or longer whip-like flagella, by 

 whose rhythmical vibrations the body of which they form part is pro- 

 pelled in definite directions. The peculiar contractility of these organs 

 seems to be an intensification of that of the general protoplasmic sub- 

 stance, of which they are special extensions. 



221. There are certain Plants, however, which resemble Animals in 

 their dependence upon Organic compounds prepared by other organisms; 

 being themselves unable to effect that fixation of Carbon by the decom- 

 position of the CO 2 of the Atmosphere, which is the first stage in their 

 production. Such is the case, among Phanerogams (flowering plants), 

 with the 'leafless parasites' which draw their support from the juices of 

 their ' hosts.' And it is the case also, among the lower Cryptogams, 

 with the entire group of FUNGI; which, however, seem generally to 

 depend rather, for their nutritive materials, upon organic matter in a 

 state of decomposition, many of them having the power of promoting 

 that process by their zymotic (fermentative) action (Chap. vn.). Among 

 Animals, again, there are several in whose tissues are found organic com- 

 pounds, such as Chlorophyll, Starch, and Cellulose, which are charac- 

 teristically Vegetable; but it has not yet been proved that they generate 

 these compounds for themselves, by the decomposition of CO 3 . 



222. The plan of Organization recognizable throughout the Vegeta- 

 ble kingdom presents this remarkable feature of uniformity, that the 

 fabric, alike in the highest and most complicated Plants, and in the low- 

 est and simplest forms of Vegetation, consists of nothing else than an 

 aggregation of the bodies termed Cells; every one of which (save in the 

 forms that lie near the border-ground between Animal and Vegetable 

 life) has its little particle of protoplasm inclosed by a casing of the sub- 

 .stance termed cellulose a non-nitrogenous substance nearly allied in 

 chemical composition to starch. The entire mass of cells of which any 

 Vegetable organism is composed, has been generated from one primordial 

 cell by processes of self-multiplication to be presently described : and the 

 difference between the fabrics of the lowest and of the highest Plants 

 essentially consist' in this, that whilst the cells produced by the self- 

 multiplication of the primordial cell of the Protophyte are all mere 

 repetitions of it and of one another, each living by and for itself those 

 produced by the like self -multiplication of the primordial cell in the 

 Oak or Palm, rtot only remain in mutual connection, but undergo a pro- 

 gressive ' differentiation/ the ordinary type of the Cell undergoing vari- 



