'STUDIES ON GERM CELLS 395 



Summary. The principal points that should be emphasized 

 are as follows: 



1. Miastor americana Felt is truly paedogenetic and agrees 

 with M. metraloas in regard to its reproduction as described by 

 Kahle ('08). 



2. One polar body, which divides by mitosis, is produced (fig. 

 30). 



3. A diminution process takes place during the division of the 

 first four cleavage nuclei in which a large part of the chromatin 

 of three of these cleavage nuclei is cast out into the cytoplasm 

 (fig. 3). 



4. One daughter nucleus of the fourth cleavage nucleus, which 

 does not lose any of its chromatin, passes into a deeply staining 

 mass of material ('polares Plasma') situated at the posterior end 

 of the egg, and is cut off from the egg by a cell wall. This cell 

 which thus contains the ^polares Plasma' and a nucleus with the 

 full amount of chromatin is the primordial germ cell (figs. 32, 

 p.g.c). 



5. A second diminution process takes place, during which each 

 of the seven somatic nuclei loses part of its chromatin and 

 emerges with one-half of the number of chromosomes. The 

 primordial germ-cell does not undergo a diminution process 

 (fig. 32). 



6. The primordial germ-cell divides by mitosis until eight 

 oogonia are produced. These separate to form two rows of four 

 oogonia each. After a long period of rest further divisions result 

 in the production of thirty-two oogonia in each germ gland. 



7. The nurse cells are of mesodermal origin. 



8. We have here for the first time a definite number of oogonial 

 divisions, namely six, a definite and equal number of oogonia 

 in each germ-gland, and a definite number of oocytes (sixty- 

 four) produced by the primordial germ-cell. It is no longer 

 necessary, therefore, to express our ignorance by saying that 

 there are n divisions during the period of multiplication of the 

 oogonia, since in Miastor the number (n) is known positively to 

 be six. 



