146 THE INDUCTIONS OF BIOLOGY. 



derived from the water by each portion of the thallus, there 

 requires no apparatus for transferring the crude food 

 materials from part to part. Among animals which, 



with but few exceptions, are, by the conditions of their 

 existence, required to absorb nutriment through one spe- 

 cialized part of the body, it is clear that there must be a 

 means whereby other parts of the body, to be supported by 

 this nutriment, must have it conveyed to them. It is clear 

 that for an equally efficient maintenance of their nutrition, the 

 parts of a large mass must have a more elaborate propelling 

 and conducting apparatus; and that in proportion as these 

 parts undergo greater waste, a yet higher development of 

 the vascular system is necessitated. Similarly with the pre- 

 requisites to those mechanical motions which animals are 

 required to perform. The parts of a mass cannot be made to 

 move, and have their movements so co-ordinated as to pro- 

 duce locomotive and other actions, without certain structural 

 arrangements; and, other things equal, a given amount of 

 such activity requires more involved structural arrangements 

 in a large mass than in a small one. There must at least be 

 a co-ordinating apparatus presenting greater contrasts in 

 its central and peripheral parts. 



The qualified dependence of growth on organization, is 

 equally implied when we study it in connexion with that 

 adjustment of inner to outer relations which constitutes Life 

 as phenomenally known to us. In plants this is less striking 

 than in animals, because the adjustment of inner to outer 

 relations does not involve conspicuous motions. Still, it is 

 visible in the fact that the condition on which alone a plant 

 can grow to a great size, is, that it shall, by the development 

 of a massive trunk, present inner relations of forces fitted to 

 counterbalance those outer relations of forces which tend con-- 

 tinually, and others which tend occasionally, to overthrow 

 it; and this formation of a core of regularly-arranged woody 

 fibres is an advance in organization. Throughout the 



animal kingdom this connexion of phenomena is manifest. 



