626 H. S. 'Jennings 



1 The "inheritance of acquired characters" meets the same 

 difficulty in the Protozoa as in Metazoa. In both Protozoa and 

 Metazoa most characteristics acquired during the Hfetime of the 

 individual are not inherited, and such inheritance does not occur 

 more readily in the one group than in the other. 



2 The difficulty with the "inheritance of acquired characters" 

 lies, not in the separation of soma and germ, but in the process 

 of cell division. If a cell bears a structure at one end, there is no 

 simple and direct reason why, when it divides, both the cells pro- 

 duced should bear the structure, and observation shows that they 

 do not, in the case of new structures. There is no evident way in 

 which a structure of this sort can overleap the barrier of cell divi- 

 sion and appear on the other side.* 



If we insist on making a comparison between the condition in 

 the Protozoa and the separation of soma and germ in the Metazoa, 

 the following is the state of the case. If any Protozoan cell (as 

 in Fig. 7) is to be divided at the next fission into two parts a and p, 

 then, so far as inheritance of new structures is concerned, a stands 

 to p as soma to germ, and reciprocally, p stands to a as soma to 

 germ. In other words, there is no evident transmission, and no 

 evident mechanism for transmission, of a new structure from a 

 to p or the reverse, just as there is no evident mechanism for trans- 

 mitting a structure from soma to germ. 



3 In order that a character may be inherited (by more than 

 one of the progeny, so as to produce a race), it must he produced 

 anew in each generation. This is what happens in the normal 

 reproduction of both Protozoa and Metazoa. 



4 In order that a new (or "acquired") character may be 

 inherited, it must be the result of such a modification of the parent 

 cell as will cause a change in the processes of reproduction; and 

 specifically, precisely such a change in these processes as will pro- 

 duce the character in question. This is equally true of Protozoa 

 and Metazoa. 



5 Most characteristics acquired during the life-time of the 



* This will be most readily grasped by looking at the figure of a typical case, such as Fig. 4, ^. Why, 

 when this animal divides transversely, should there be a spine upon the posterior (left) half, as well as 

 upon the anterior (right) ? As a matter of fact, there is not. 



