THE BEGINNINGS OF II FE. 255 



in which their ingredients are contained ? How can 

 we imagine that such specific shapes as rhomboid 

 dodecahedrons or octahedrons are enabled to appear 

 de novo in homogeneous solutions ? Have we not 

 here facts of almost the same order ? Familiarity with 

 such occurrences, as actual and recognized phenomena_, 

 is apt to dim our mental vision, so that we pay no 

 heed to what must have been the primary difficulty 

 of the conception. Yet the fact that such definite and 

 specific forms do spring up in solutions, whenever the 

 suitable conditions exist, is doubted by none. The 

 chemist explains it as well as he can. And if, in so 

 doing, he is allowed, from the necessities of the case, 

 to postulate the existence of inherent tendencies and 

 molecular affinities to account for the particular forms 

 assumed by his cohering molecules, why, by the name 

 of all that is fair in Science, may not the biologist 

 be allowed to resort to similar explanations as to the 

 rationale of a process which, though at present un- 

 familiar to many, is nevertheless as much a matter of 

 fact as the process of crystallization itself? Does not 

 the chemist find that the form of a crystal, of any given 

 substance, may vary according to the particular com- 

 bination of conditions under which it is produced — and 

 that within no very narrow limits ? And when we 

 have to do with matter of a higher, more complex, and 

 more unstable character, is it not to be supposed that 

 the limits of possible variation would increase in a 

 more than proportionate ratio ? So that from what we 



