JrXE 7, 1895.] 



SCIENCE. 



619 



where, as in the bauaua, it has maiutaineil 

 its unabated vigor for probably not less 

 than two thousand years without the help 

 of sexual reproduction. In many organisms 

 the germinal elements must grow and be- 

 come mature. While in the immature 

 state they do not, for the moment, have the 

 latent potentialitj' of germs that can, then 

 and there, develop, but may even be de- 

 stroyed phagocytically, or absorbed by other 

 non-germinal tissues. In still other cases 

 there is no proof that the germinal matter 

 is difterentiated, as a complete mechanism, 

 from the first stages of ontogeny onwards, 

 so that the theory of its continuity is not 

 only not always true but is also of small 

 importance. At anj- rate, it is of far less 

 importance than the fact of continuous 

 metabolism and the gradual advent of 

 monotropism, from a state of germinal ;eolo- 

 tropism, efl'ected by the dj^namical process 

 of tissue metamorphosis and specialization. 

 This development of monotropism cannot 

 take place e.xcept through the sorting and 

 grouping of specialized molecules, under 

 the domination of forces, the operation of 

 which remains to be discovered in the laws 

 of physiological chemistry and molecular 

 mechanics, and not by an appeal to an un- 

 workable hypothesis that merely covers up 

 our ignorance and impedes our progress by 

 invoking the help of ' gemmules ' or ' bio- 

 phors ' that grow and divide like cells. 

 There is no evidence that will enable us to 

 conceive the growth of the molecules of 

 living matter in this way, since we are now 

 dealing with very complex metameric mole- 

 cular bodies,. the growth and disintegration 

 of which is probably essentially similar to 

 the gi-owth and solution of crystals, during 

 the process of metabolism, with this ditfer- 

 ence that growth and disintegration go on 

 at the same time in living bodies. "We do 

 not even know the real nature of the 

 chemical changes that go on in these mole- 

 cules and determine their structure. That 



the forces that do determine this are of a 

 chemical nature, operating under very pecu- 

 liar conditions, we may be certiiin. The 

 complexity of these bodies, and their com- 

 plex 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 iiueven 

 part of the oosperm (Loeb), will operate in 

 the same way as the whole. If we accept 

 the dynamical hjijothesis 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 de- 

 terminants.' The arithmetical impassibility 

 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 

 determinants ' were unequally divided . 



Regenei-ation is also to be explained upon 

 the basis of a dynamical theory, as well as 

 polj'morphism, alternation of generations, 

 reversion, and so on. We find indeed that 

 it is only the same kind of tissue that will 

 regenerate the same sort after development 

 has advanced a considerable way. Mono- 

 tropism has been attained by each kind of 

 tissue, and this prevents the production of 

 anj-thing else but the one sort, in each case, 

 after tissue diiferentiation has proceeded a 

 little way. Polymorphic 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 

 transformation of which is not told oft" in a 

 single generation, but in the course of sev- 

 eral distinct ones. Sex itself is thus de- 

 termined and must in some way depend 

 upon subtle disturbances of the transforma- 



