1896.] Sex Cells in Cymatogaster. 269 



when sex cells are present without regard to whether this po- 

 sition is normal or not. 5 If the sex cells thus influence the 

 surrounding tissue, may we not safely assume a reciprocal in- 

 fluence of the surrounding tissues on the reproductive cells? 



Sexuality can first be distinguished not by the difference in 

 the sex cells, but by the character of the peritoneal covering. 

 While this difference in the peritoneal covering may be the 

 expression of an invisible difference existing in the repro- 

 ductive cells, it is quite possible that sex is determined by 

 the body. In frogs, butterflies, etc. the sex determining power 

 of the soma has been experimentally demonstrated. Later it 

 is well known that the character of the sex cells influences 

 the remotest parts of the organism, although we are not at all 

 familiar with the processes by which this is accomplished. 



Changes in the sex cells introduced by the body which do 

 not become apparent until the development of the cells into 

 young, seem, therefore, to be not impossible, although we are 

 entirely unable to tell just how such a change might be ac- 

 complished. 



Since writing the above, I have received, through the kind- 

 ness of the author, Dr. Minot's " Ueber die Vererbung und Ver- 

 jiingung." While the views expressed are not identical with 

 those given in the present chapter, there is considerable agree- 

 ment. Dr. Mmot recognizes that the problem of the origin of 

 the reproductive cells is also the problem of the origin of the 

 tissue cells (p. 580), and that " a germ plasm in the Weismann- 

 ian sense does not exist." So far we agree. According to him 

 all parts inherit from the germ and possess, as well as the re- 

 productive cells, the power of multiplying and morphogenesis, 

 but this power cannot manifest itself on the part of the somatic 

 cells because the conditions of the body prevent it. The con- 

 ditions are the increased amount of protoplasm and the 

 specialization of the tissues. According to my views it is not 

 so much a high state of tissue differentiation which holds cap- 

 tive the morphogenic power in muscle cells for instance as it 



and situated in front of the normal position, 

 about these sex cells entirely independent ol 

 occurring in the normal place. 



