Heredity. 153 



is nothing more than the resultant of the forces which 

 maintain the chemical species of which the organism is 

 composed." 



What may be called the dominant modern view is 

 summed up in the word organization. What the germ- 

 cell inherits from the parental germ-cells is an organiza- 

 tion of great complexity. Of the nature of this organi- 

 zation we know nothing, but it is possible to think of it 

 as an intricate architecture of minute particles which 

 are the material bearers of particular qualities. To 

 these hypothetical units numerous names have been 

 given biophors, pangenes, idiosomes, &c. &c. 



The doctrine of the continuity of the reproductive 

 protoplasm not only answers the first question as to 

 the uniqueness of the germ-cell, but thereby The Problem 

 casts a new light upon the problem of recon- of Recon- 

 struction. The problem is simplified, and, structlon - 

 to a certain extent, disappears. Why should the germ- 

 cell divide, redivide, and build up an embryo in the 

 precise way in which it does? Because it is virtually 

 continuous with the parent germ, which behaved in a 

 precisely similar fashion. Thus the question ceases to 

 be particular, and becomes general ceases, in fact, to 

 be a problem in heredity, and becomes a subject for 

 investigation under the mechanics of development. 



This, it need hardly be said, is to refer to a field of 

 investigation which has been but little worked. In spite 

 of the luminous suggestions of His, Rauber, Roux, and 

 others, there are few general facts on which one can 

 find foothold for further construction. Yet the task has 

 been more than begun in the investigations of the en- 

 thusiastic modern school of experimental embryologists. 

 Such current phrases as " cellular dynamics", "proto- 

 plasmic mechanics", "developmental mechanics", "phy- 

 siological morphology", indicate the trend of modern 

 research. 



"To think that heredity will build organic beings 

 without mechanical means is a piece of unscientific mys- 

 ticism ", as Professor His has said, and yet the tendency 

 does not rapidly disappear from even scientific literature. 

 To say that "ontogeny recapitulates phylogeny", or 



