140 THE BIOLOGICAL PROBLEM OF TO-DA Y 



the many problems involved in the course of organic 

 development. In this respect it differs from 

 Weismann's doctrine of determinants, as that 

 is a closed system, finding within itself a formal 

 explanation of all development. So far it seems to 

 me an abandonment of explanation rather than an 

 explanation ; for it explains by signs and tokens 

 that elude verification and experiment, and that 

 cannot encounter concrete investigation. His ex- 

 planation is no more than a description, in other 

 words, of the visible events of development. To be 

 more than this, it would be necessary to explain 

 how in each case the biophores and determinants 

 and ancestral plasms are constituted, and how they 

 are arranged in the architecture of the germplasm 

 so as to produce the development of the egg- cell in 

 this or that fashion. It must, at the least, offer 

 such possibilities as the structural formulae of 

 chemists offer. But in the present stage of our 

 knowledge Weismann's method is unpromising ; 

 it merely transfers to an invisible region the 

 solution of a problem that we are trying to solve, 

 at least partially, by investigation of visible char- 

 acters ; and in the invisible region it is impossible 

 to apply the methods of science. So, by its very 

 nature, it is barren to investigation, as there is no 

 means by which investigation may put it to the 

 proof. In this respect it is like its predecessor, 

 the theory of preformation of the eighteenth 

 century. 



