VIIL] HOMOLOGIES. 201 



to be accompanied by any corresponding differentiation of 

 function between different parts ; and, so far as I can see, 

 the beautiful regularity and symmetry of their radiated 

 forms are altogether due to unknown laws of symmetry of 

 growth, just like the equally beautiful and somewhat similar 

 forms of the compound six-rayed, star-shaped crystals of 

 snow." 



Altogether, then, it appears that each organism has an 

 innate tendency to develop in a symmetrical manner, and 

 that this tendency is controlled and subordinated by the 

 action of external conditions, and not that this symmetry is 

 superinduced only ab externo. In fact, that each organism 

 has its own internal and special laws of growth and devel- 

 opment. 



If, then, it is still necessary to conceive an internal law 

 or " substantial form," moulding each organic being, 41 and 

 directing its development as a crystal is built up, only in 

 an indefinitely more complex manner, it is congruous to im- 

 agine the existence of some internal law accounting at the 

 same time for specific divergence as well as for specific 

 identity. 



A principle regulating the successive evolution of differ- 

 ent organic forms is not one whit more mysterious than is 

 the mysterious power by which a particle of structureless 

 sarcode develops successively into an egg, a grub, a chrysalis, 

 a butterfly, when all the conditions, cosmical, physical, 

 chemical, and vital, are supplied, which are the requisite 

 accompaniments to determine such evolution. 



41 It is hardly necessary to say that the author does not mean that 

 there is, in addition to a real objective crystal, another real, objective 

 separate thing beside it, namely the " force " directing it. All that is 

 meant is that the action of the crystal in crystallizing must be ideally 

 separated from the crystal itself, not that it is really separate. 



