THE GERM PLASM TilKOin 291 



tureless body from wliicli holli I lie body .ind the ova 

 of the individual evolve; and considered lliese ova 

 to consist of contributions partly from I he v<n^ and 

 partly from the body which develoix'd from the e^'^'. 

 Later Jager (1877) stated the idea of gerim'nal con- 

 tinuity more definitely. He maintained that |)art 

 of the germ-plasm (Keini Protoplasma) of the 

 animal forms the individual, and the rest is re- 

 served until sexual maturity, when it forms the re[)ro- 

 ductive material. The reservation of this j)hyl()- 

 genetic substance he termed the "continuity of 

 the germ-plasm" ("Continuitiit des Keimproto- 

 plasmas"). To Weismann (1885) is usually givtMi 

 the credit for originating the germ-j)lasui theory, 

 but while w^e are undoubtedly iiKh'bted lo him for 

 the great influence the hyj^othesis of germinal con- 

 tinuity has had upon the trend of biological in\ (•>({- 

 gations within the past thirty years, we must con- 

 sider Jager as the first to clearly enunciate I he i(N a. 

 Jager (1878) also expressed a belief in the mor- 

 phological continuity of the germ cells of succeed- 

 ing generations, but this idea was first definitely 

 stated by Nussbaum (1880), whose investigations 

 of the germ cells in the trout and I'log led him to 

 conclude that the cleavage cells t'orni two groups 

 independent of each other. One group contains 

 the cells which multi})ly and dill'erent iate and Ihns 

 build up the body of the individual, but do not |)i'o- 

 duce germ cells; the other group takes no pari in 

 the formation of the body and undergoes no ditl'eren- 

 tiations, but mult ij)lics by simple division. The germ 



