296 NATHAN FASTEN. 



trite remarks on page 402 : ' The nature of the chromatoid body 

 thus remains problematical, but the facts are worthy of serious 

 attention for another reason. Were the chromosomes very small, 

 numerous, closely crowded, or otherwise unfavorable for exact 

 study, and could not the entire history of the chromatoid body 

 be so clearly traced, even an experienced observer might fall into 

 the most confusing error concerning the relations of the chro- 



mosomes.' 



7. SUMMARY. 



I.. During the latter part of June and the early part of July 

 the testicular lobes of Cancer magister are in the best shape for 

 the study of spermatogenesis. 



2. Two spermatogonial divisions can be recognized, and these 

 ultimately form the resting primary spermatocytes. 



3. Sometimes, larger and more intensely staining cells are 

 found interspersed among the spermatogonia. These are the 

 nutritive cells, and it seems very probable that they have origi- 

 nated from a transformation of some of the spermatogonia. 

 The nuclei of the nutritive cells are irregular in shape and many 

 of them possess amoeboid processes. In sections of some of the 

 nutritive cells two or more nuclei are oftentimes found, and this 

 might easily mislead one into concluding that amitosis occurs 

 amongst them. 



4. The resting primary spennatocyte undergoes a growth 

 period, during which thin leptotene threads are produced through 

 the fragmentation of the chromatin. No continuous spireme 

 is formed as the leptotene threads appear distinct and separate. 



5. During the growth period pairs of leptotene threads migrate 

 to the synaptic pole of the cell, become arranged in parallel 

 fashion and soon fuse parasynaptically. 



6. During the synizesis stage of the growth period a pair of 

 densely staining chromatoid bodies make their appearance in the 

 cytoplasm. These are surrounded by clear areas and may have 

 originated from some of the chromatoid masses found within the 

 cytoplasm of some of the earlier stages in the spermatogenesis. 



7. The first spermatocyte division is reductional. In the 

 metaphase stage the chromosomes line up as dumb-bells, which 

 are composed of pairs of bivalents. The chromatoid bodies pass 

 undivided to opposite poles of the cell. 



