20 CALIFORNIA ACADEMY OF SCIENCES. 



continuity with the germinal cell from which they, in 

 common with all the cells of the organism, derive their 

 origin. In this sense there is a true continuity of germ- 

 cells." 



Morgan, like Ryder, believes the reproductive cells 

 have been set apart in the division of labor, and in 

 this he is in accord with Weismann. The agreement 

 is not carried out in the details, however. Morgan says:* 

 " Cell-reproduction is, however, in the metazoa of two 

 kinds. There is the direct reproduction of differentiated 

 cells, by which muscle-cells, nerve-cells, or others re- 

 produce their kind in the growth of tissues or organs; 

 and there is the developmental reproduction, by which 

 the germinal cells under appropriate conditions repro- 

 duce an organism similar to the parent. The former is 

 in the direct line of descent from the simple reproduc- 

 tion of amoeba. The latter is something peculiarly 

 metazoan, and is, if one may be allowed the expression, 

 specialized in its generality." 



Prof. Eimerf expresses himself in similar terms with 

 regard to the continuity of body cells. He says: " If 

 the body of the multicellular organism is thus, even 

 according to Weismann's ideas, of secondary importance 

 in comparison with the germ-plasm, if the latter corres- 

 ponds to the unicellular organism, it follows that the 

 multicellular is just as immortal or mortal as the uni- 

 cellular. And thus it is impossible to see why, between 

 the germ-plasm of the multicellular on the one haiid^ 

 and that of the unicellular on the other, there should 

 exist this profound difference, that the latter acquire 

 characters during life and transmit them by heredity, 

 the former not, how the former any more than the 



* 1. c., p. 143. 



t Organic Evolution; English Translation, p. 71. 



