40 BIOLOGICAL LECTURES. 



peculiar conditions, we may be certain. The complexity of 

 these bodies, and their complex relations to one another, give 

 us all the mechanism we need in order to account for the 

 phenomena of heredity. 



One-half, or one-quarter, or an uneven part of the ob'sperm 

 (Loeb) will operate in the same way as the whole. If we ac- 

 cept the dynamical hypothesis here proposed we are relieved 

 of going to the length of the absurdity of assuming that by 

 dividing a germ we multiply its " biophors " as many times by 

 two as we have made divisions, or of postulating " double," or 

 " quadruple determinants." The arithmetical impossibility of 

 multiplying by a process of division is, as we see in this case, 

 too much for any non-dynamical corpuscular hypothesis. 

 Where the division of the germ is unequal, as in some of 

 Loeb's experiments, we should, on the basis of a preformation 

 hypothesis, be compelled to suppose that the " double determi- 

 nants" were unequally divided. 



Regeneration is also to be explained upon the basis of a dy- 

 namical theory, as well as polymorphism, alternation of genera- 

 tions, reversion, and so on. We find indeed that it is only the 

 same kind of tissue that will regenerate the same sort after 

 r development has advanced a considerable way. Monotropism 

 I has been attained by each kind of tissue, and this prevents the 

 I production of anything else but the one sort, in each case, 

 I after tissue differentiation has proceeded a little way. Poly- 

 morphic or metagenetic forms are to be accounted for in the 

 same way as constantly repeated ones. Like the latter they are 

 produced by the operation of a molecular mechanism, the story 

 of the transformations of which is not told off in a single gener- 

 ation but in the course of several distinct ones. Sex itself is 

 thus determined and must in some way depend upon subtle 

 disturbances of the transformation of the molecular mechan- 

 ism of the germ, the nature of which is still quite unknown 

 to us. 



Equally remarkable are the phenomena of heteromorphosis 

 described by Loeb, whose experiments prove that some ani- 

 mals, like most vegetable organisms, may adjust the molecular 

 machinery of their organization in any new direction what- 



