46 PETER OKKELBERG - 



In the lamprey, according to evidence presented above, most 

 of the somatic part of the germ gland comes from the perito- 

 nemn. This is certainly true of the follicular epithelium and a 

 considerable portion of the interfoUicular tissue. On the other 

 hand, some mesenchyme is included in the gland fold as it is 

 formed and some is carried in later by the blood-vessels. 



WTiether or not the follicular cells take any active part in 

 nourishing the germ cells in the early stages is not known. The 

 only case of a true nurse cell observed in the germ gland of lower 

 vertebrates in early stages is that described by Kuschakewitsch 

 ('10). He found what he considered to be nurse cells in frog 

 larvae which developed from his so-called ' Spatbefruchteten' eggs. 

 They were distinguished by greatly concentrated nuclei and by 

 cytoplasm filled with granules which he thinks are chromidia. 

 These nurse cells were not, according to him, themselves used as 

 food for the neighboring germ cells, but served as a source of 

 certain ferments which were useful in preparing nourishment 

 for the cells. He says concerning them: ''Es handelt sich aber 

 um eine Sezernierung von Fermenten, welche es bewirken dass 

 die in der Keimanlage zirkuherenden Nahrstoffe von den Ampul- 

 lenelementen besser ausgeniitzt werden konnen." 



A proliferation of peritoneal cells to form follicle cells has 

 been observed by other investigators in various groups of verte- 

 brates other than the cyclostomes. In the frog it has been 

 observed by Bouin ('01), Dustin ('07), Kuschakewitsch ('10), 

 and others. Bouin believes that these cells take part in the 

 formation of germ cells as well as foUicle cells. Kuschakewitsch 

 does not believe that they take part to any great extent in the 

 formation of germ cells. Dustin states that he observed the 

 transformation of ordinary peritoneal cells into germ cells in the 

 turtle (Chrysemys). Allen ('06), however, working on the same 

 form, found no evidence of such transformation. In Triton, 

 Abramowicz ('13) observed the proliferation of peritoneal cells 

 in the germ gland, and beheves that these cells give rise to 

 folUcle cells and interfoUicular tissue as well as to germ cells, and 

 to the cells of the sex cords. King ('08) thinks that in Bufo 

 lentiginosus the peritoneal cells give rise to all the elements of 

 the sex gland with the exception of the germ cells. 



