384 RECORDS. 



or potentiality of the uhole organism, but the cells assume 

 specific characters according to the protoplasmic stuffs allotted 

 to them (Fig. 3, ^). 



This attempt to portray briefly the modus operandi oi devel- 

 opment is doubtless an excessively naive mode of formulating a 

 highly complex and subtle process, concerning the real nature 

 of which we still know very little. Even if literally correct it 

 would still leave quite out of account some of the most impor- 

 tant elements of our problem. I do not offer it as a well-estab- 

 lished or fully rounded conclusion, but rather as a convenient 

 way of placing before you one fundamental result, towards w^hich 

 I believe the drift of recent research is tending. This is that the 

 germ consists of two elements, one of which undergoes a devel- 

 opment that is essentially epigenetic, while the other represents 

 an original controlling and determining element. The first is 

 represented by the protoplasm of the ^^%. The second is the 

 nucleus, which, as I have attempted to show, must apparently 

 be conceived as a kind of microcosm or original preformation, 

 consisting of elements which correspond, each for each, to par- 

 ticular parts or characters of the future organism. The actual 

 development of the embryo, which is manifested by progressive 

 changes in the protoplasm, is by epigenesis, as Harvey and 

 Wolff maintained. Its primary determination is by means of a 

 preformed apparatus, handed on to the egg from preceding gen- 

 erations in the nucleus, which, though not in any sense a min- 

 iature model of the adult, yet somehow embodies in infinitesimal 

 compass, the heritage of the race. And thus the most recent 

 discoveries in this difficult field of research are bringing us to a 

 position which can hardly be better stated than in the words 

 written by Huxley more than thirty years ago : *' The process 

 which in its superficial aspect is epigenesis appears in essence to 

 be evolution. . . . and development is merely the expansion of 

 a potential organism or original preformation according to fixed 

 laws." We should not, with the advantage of our present 

 standpoint, read into these words of Huxley's a meaning which 

 it was impossible that he should have had in mind in writing 

 them ; yet without yielding to this temptation we may fairly 



