STUDIES ON GERM CELLS 391 



found in stages earlier than the four-cell stage, but are present 

 in many of the later stages (figs. 32, 33, 34, 35, 36, cR) and are 

 called by Kahle 'Chromatinreste.' One daughter nucleus result- 

 ing from the division of nucleus iv (fig. 3) becomes imbedded in 

 the 'polares Plasma' and, with this substance, is cut off from the 

 rest of the egg as the primordial germ-cell (fig. 32, p.g.c). The 

 other daughter nucleus of spindle iv remains in the egg. These 

 two nuclei are the only ones at this stage which contain a complete 

 amount of chromatin. 



During the next stage (viii-xv) the daughter nucleus of cleav- 

 age cell IV, which remains in the egg, undergoes a diminution 

 process whereby it loses part of its chromatin, • and the other 

 six nuclei within the egg pass through a second diminution pro- 

 cess during which a second 'Chromosomenmittelplatte' is formed 

 (figs. 32 and 4, cMp). At the fifteen-cell stage, therefore, one 

 nucleus (that of the primordial germ-cell, fig. 32, p.g.c.) contains 

 the full amount of chromatin; whereas all of the others (somatic 

 nuclei) have lost a large portion of their chromatin. After the 

 second diminution process, according to Kahle, the somatic 

 nuclei possess only half the number of chromosomes present in 

 the germ cells, that is "der Diminutionsprocess und der Reduc- 

 tionsprocess in derselben Karyokinese verenigt sind." My 

 material did not contain enough of the early cleavage stages 

 to enable me to confirm in detail Kahle's investigations, but one 

 egg contained well marked mitotic figures which represent 

 stages in the second diminution process (fig. 32) and a large num- 

 ber of sections were obtained which contained chromatin masses 

 ('Chromatinreste,' figs. 32, 33, 34, 35, 36, cR). The details of 

 the second diminution process are shown in figure 4. 



The history of the germ-cells, from the time of the formation 

 of the primordial germ-cell to the production of the sixty-four 

 oocytes contained in the two ovaries, thirty- two in each, will now 

 be described briefly. 



The somatic nuclei divide rapidly, forming the blastoderm as 

 shown in figures 33 and 34. Chromatin masses (cR.) repre- 

 senting chromatin cast out during the diminution processes are 

 present in these early stages. The primordial germ-cell (fig. 32, 



JOUR>fAL OP MORPHOLOGY, VOL. 25, NO. 3 



