PRESIDENTIAL ADDRESS. 39 



ter of similar cells, but these units soon lost their original 

 homogeneity. As the result of mere relative position, some of 

 the cells were especially fitted to provide for the nutrition of 

 the colony, while others undertook the work of reproduction. 

 Hence the single group would come to be divided into two 

 groups of cells, which may be called somatic and reproductive — 

 the cells of the body as opposed to those which are concerned 

 with reproduction (p. 27) , . . As the complexit}- of the 

 metazoan body increased, the two groups of cells became more 

 sharply separated from each other. Very soon the somatic 

 cells surpassed the reproductive in number, and during the in- 

 crease they became more and more broken up by the principle 

 of the division of labor into sharply separated systems of tis- 

 sues. As these changes took place the powxr of reproducing 

 large parts of the organism was lost, while the power of repro- 

 ducing the whole individual became concentrated in the repro- 

 ductive cells alone " (p. 28). His theory further assumes that 

 the germ-cells contain two kinds of plasm, which he calls re- 

 spectiveh' the ovogenetic and the somatogenic, i. e., the first 

 capable onh- of producing germ-cells, the latter capable only 

 of producing somatic cells. These exist together in the fertil- 

 ized ovum, and if allowed to remain there would go on repro- 

 ducing themselves in something like equal numbers. But the 

 bod}^ consisting almost entirely of somatic cells, it is evident 

 that such a multiplication of germ-cells would be onh- a hin- 

 drance to development. This, he claims, explains the myste- 

 rious phenomena so long observed by embryologists and called 

 the removal of polar bodies. The polar body first removed is 

 nothing more nor less than the ovogenetic nucleo-plasm, which 

 is now in the way, and whose removal is necessary to the 

 formation of the embryo. This is the work alone of the somatic 

 cells, and these, consisting as they do of the germ-plasms of an 



