CHAP, xiii.] THE GAT'S PLACE IN NATURE. 447 



as the melon cactus, are not arborescent, but assume a spheroidal 

 figure. 



As to modes of reproduction, no absolute distinction can be 

 drawn between plants and animals. For many animals reproduce 

 by budding (as do zoophytes), and some may even be propagated by 

 cuttings. Thus if the Hydra, or the common sea-anemone (Anthed), 

 be bisected, each half soon grows into the perfect form once more, 

 and many worms (such as Scyllis and Catenuld), and animalcule 

 called Infusoria, habitually multiply by self-made sections, i.e., by 

 spontaneous self-division or " fission." ISTot only, moreover, is 

 sexual reproduction as universal amongst plants as amongst animals, 

 but even male mobile filaments, closely resembling spermatozoa, are 

 developed by very many flowerless plants. 



As to the different modes of feeding practised by plants and 

 animals, imbibition is indeed (as has been said) universal with the 

 former. But then the digested insects made use of by Drosera and 

 Dioncea may be said to be taken into a temporary quasi-cavity, while 

 in certain other plants the receptacle has the form of a permanent 

 sac. This is the case with the curious pitcher plant (Nepenthes), in 

 the pitchers of which insects are caught and decomposed, probably to 

 the profit of the plant.* But not all animals take solid food into an 

 internal cavity or stomach. Many can only imbibe it through the 

 outer surface of their bodies. It is thus that tape-worms (which lie 

 perennially bathed in a fluid medium unceasingly nutritious) feed. 



Lastly, we come to the distinction between animals and plants as 

 regards their chemical composition. Xow it is true that most plants 

 are less nitrogenous than are animals. But this cannot be affirmed 

 of the great group of Fungi. Moreover, substances which were long 

 deemed peculiar to the vegetable kingdom, are now known not to be 

 so. Thus, " starch," e.g., has been found even in the human brain ; 

 while " cellulose " the principle of wood exists in the tough 

 external coat which invests the bodies of the Tunicates before 

 referred to. 



Thus all the foregoing six distinctions break down with respect to 

 a considerable number of animals or plants, though they may serve 

 to separate all the higher forms of the two kingdoms of living 

 beings. 



Other distinctions, however, exist which have a greater value, and 

 may be conjointly made use of in discriminating almost all plants 

 from all animals. Of these there are two the first (A) relates to 

 structure ; the second (B) relates to function. 



A. It has been already said that every living organism consists of 

 a substance called protoplasm, with which other substances (some 

 nitrogenous, some non-nitrogenous) may co-exist. Amongst the 

 non-nitrogenous occasional accompaniments of protoplasm is 

 " cellulose." 



* The structures referred to are curious pitcher-like productions which are formed 

 at the end of foliage leaves. 



