486 ROBERT W. HEGNER 



3. In Miastor there are a definite number of cell divisions 

 during the multiplication of the oogonia, namely, six. The 

 somatic cells lose part of their chromatin by diminution processes, 

 whereas the germ cells possess a complete amount of chromatin. 

 The nurse cells are of mesodermal origin. A peculiar mass of 

 cytoplasm becomes situated at the posterior end of the oocyte; 

 within this one of the first eight cleavage nuclei (with a complete 

 amount of chromatin) becomes imbedded; it is then cut off from 

 the rest of the egg as the primordial germ cell. The origin of 

 this peculiar mass of cytoplasm could not be determined, but 

 several hypotheses are offered "to account for its genesis (figs. 

 27-40, 3-5, pp. 387-398). 



4. The eggs of the ovoviviparous dipteron, Compsilura and of 

 the willow-cone gall fly, Cecidomyia, contain Keimbahn-determi- 

 nants which have a history like that of similar bodies in other 

 insects (figs. 41^3, 6, pp. 398-399). 



5. An early segregation of germ cells has been reported for 

 certain Chrysomelid beetles and Keimbahn-determinants have 

 been found in the eggs of those carefuly examined. A resume 

 of the writer's previously published results is given (figs. 7-8, 

 pp. 400-408). 



6. An examination of all stages in the early cleavage of Chry- 

 somelid eggs failed to reveal a chromatin-diminution process 

 such as occurs in Ascaris and Miastor. The conclusion is reached 

 that the cleavage nuclei are all potentially alike and that the cyto- 

 plasm controls their differentiation into the nuclei of blastoderm 

 cells, primordial germ cells, and vitellophags. What appears to 

 be amitotic nuclear division among the vitellophags is described 

 (figs. 44-57, 7-8, pp. 408-413). 



7. No nuclear changes were observed in the germ-cell cycle 

 of Leptinotarsa resembling those recorded by Giardina ('01) 

 and others in Dytiscus resulting in the formation of nurse cells 

 and ultimate oogonia (pp. 413-417). 



8. The pole-disc granules in Chrysomelid eggs form a recogniz- 

 able mass, just before the oocyte reaches its full size. This 

 genesis could not be definitely determined, but several methods 

 of origin are suggested. The growth of the oocyte is described 

 and figured (figs. 58-66, 9, pp. 417-420). 



