ASSOCIATION OF SOMATIC AND GERM CELLS IN 



CESTODES. 



R. T. YOUNG. 



The differentiated tissues of cestodes all arise from the paren- 

 chyma, primarily of the larva and secondarily of the adult. 

 From this are formed the sex cells, there being no evidence 

 whatever to indicate any specialized "germ path" or "germ 

 cell determinants." One author 1 indeed has gone so far as to 

 claim that specialized cells (muscle) may even be de- and redif- 

 ferentiated to form germ cells. 



How far these observations of Child are valid is open to ques- 

 tion. His figures certainly give considerable support to his 

 contention, but it is difficult to prove that any muscle directly 

 contiguous to a developing testis is responsible for the origin of 

 the latter, or that the testis represents its original myoblast. 

 The contiguity may be accidental, and the parent muscle cell 

 may lie at a different place and be separated from the muscle 

 fibre by a considerable space, being connected to it by only a 

 slender process. The occurrence of multinucleate myoblasts, 

 some of which Child has figured and which I have occasionally 

 found in my own slides, renders his interpretation reasonable, 

 but by no means proves it. 



The occurrence of fully differentiated flame cells within the 

 testis of several species 2 of cestodes, unconnected with any other 

 flame cells or excretory capillaries is suggestive, although not 

 proof of a common origin of these cells. It is quite possible that 

 the flame cells may have arisen outside of the testis and migrated 

 into the latter secondarily, or the testis and flame cell may have 

 developed side by side, the latter becoming surrounded by the 

 offspring of the former. 



1 Child, C. M., "Studies on the Relation between Amitosis and Mitosis, II., 

 Development of the Testis and Spermatogenesis in Moniezia, BIOL. BULL., XII. 

 175-212. 



2 Rhyncobothrium bulbifer, Dipylidium caninum and an undetermined species 

 from a woodpecker (Dryobates). 



312 



