DIFFERENCES BETWEEN ANIMALS AND PLANTS. 9 



matter of plants. Any organism which exhibits chlorophyll 

 in any quantity, as a proper element of its tissues, is most 

 probably vegetable. As in the case of cellulose, however, the 

 presence of chlorophyll cannot be looked upon as a certain 

 test, since it occurs normally in certain undoubted animals 

 (e.g., Stentor, amongst the Infusoria, and the Hydra viridis, 

 or the green Fresh-water Polype, amongst the Ccclenteratd). 



d. Motor Power. This, though broadly distinctive of ani- 

 mals, can by no means be said to be characteristic of them. 

 Thus, many animals in their mature condition are permanently 

 fixed, or attached to some foreign object ; and the embryos of 

 many plants, together with not a few adult forms, are endowed 

 with locomotive power by means of those vibratile, hair-like 

 processes which are called "cilia," and are so characteristic 

 of many of the lower forms of animal life. Not only is this 

 the case, but large numbers of the lower plants, such as the 

 Diatoms and Desmids, exhibit throughout life an amount 

 and kind of locomotive power which does not admit of being 

 rigidly separated from the movements executed by animals, 

 though the closest researches have hitherto failed to show the 

 mechanism whereby these movements are brought about. 



e. Nature of the Food. Whilst all the preceding points 

 have failed to yield a means of invariably separating animals 

 from plants, a distinction which holds good almost without 

 exception is to be found in the nature of the food taken 

 respectively by each, and in the results of the conversion of 

 the same. The unsatisfactory feature, however, in this dis- 

 tinction, is this, that even if it could be shown to be, theoreti- 

 cally, invariably true, it would nevertheless be practically 

 impossible to apply it to the greater number of those minute 

 organisms concerning which alone there can be any dispute. 



As a broad rule, all plants are endowed with the power of 

 converting inorganic into organic matter. The food of plants 

 consists of the inorganic compounds, carbonic acid, ammonia, 

 and water, along with small quantities of certain mineral salts. 

 From these, and from, these only, plants are capable of 

 elaborating the proteinaceous matter or protoplasm which 

 constitutes the physical basis of life. Plants, therefore, take 

 as food very simple bodies, and manufacture them into much 

 more complex substances. To this general statement, however, 

 an exception must seemingly be made in favour of certain fungi, 

 which require organised compounds for their nourishment. 



On the other hand, no known animal possesses the power 

 of converting inorganic compounds into organised matter, but 

 all, mediately or immediately, are dependent in this respect 



