STUDIES ON GERM CELLS 487 



9. In the testis of Leptinotarsa the germ cells in each cyst 

 arise from a single spermatogonium. Spindle remains connect 

 the daughter spermatogonia up to the time when sixty-four cells 

 are present in each cyst. This process is homologous to the 

 differential divisions in Dytiscus and other beetles, and certain 

 Hymenoptera, during which an ultimate oogonium and a def- 

 inite number of nurse cells arise from a single oogonium (figs. 

 68-74, 10-12, pp. 420-424). 



10. What appears to be amitotic muclear division was found 

 among the nurse cells of Leptinotarsa, but no nuclear phenomena 

 were observed among the oogonia or spermatogonia which 

 could be interpreted as amitosis and which could not be regarded 

 as phases of mitosis (fig. 67, p. 427.) 



11. A brief statement is given of certain phenomena that have 

 been recorded during the segregation of the germ cells in the 

 Hymenoptera (figs. 13-14, pp. 428-432). 



12. The Keimbahn in the Crustacea is best known in certain 

 Cladocera and Copepoda. In some species the Keimbahn- 

 determinants seem to be temporary bodies which represent the 

 "Endprodukte des Kern-Zelle-Stoffweschsels." In others they 

 appear to originate from nurse cells which enter the oocyte 

 (figs. 15-18, pp. 432-441). 



13. In several species of Ascaris a determinate segregation of 

 germ cells has been recorded and a chromatin-diminution proc- 

 ess discovered. The most recent work indicates that this dimi- 

 nution process is controlled by the cytoplasm and is not initiated 

 by the nuclei (figs. 19-21, pp. 442-446). 



14. The origin of the 'besondere Korper,' which serves as a 

 Keimbahn-determinant in Sagitta, has not been determined. 

 It apparently is unequally distributed when the primordial 

 germ cell divides, and the daughter cell which receives the larger 

 portion is considered the primordial spermatogonium; the other 

 is the primordial oogonium (figs. 22, pp. 446-449). 



15. The vertebrates do not furnish as favorable material for 

 germ cell studies as do the invertebrates. No definite Keim- 

 bahn-determinants have been discovered in them but bodies 

 have been described in the cell body of some of them which give 



JOURJfAL OF MORPHOLOGY, VOL. 25, NO. 3 



