SPERMATOGENESIS IN THE ALBINO RAT 169 



is 0.244 grams, as compared with 0.067 at 14 days (Donaldson, 

 '15). The weight of the organ from the time when the pachytene 

 cells are well developed until the first crop of spermatozoa is 

 produced is thus almost quadrupled. 



I have found in the literature no other account of the age at 

 which the various steps in the process of spermatogenesis occur. 



The age of 37 days for the first crop of spermatozoa correlates 

 closely with the time of descent of the testes, which occurs 

 "about the fortieth day of age or somewhat earlier" (Donaldson, 

 '15). 



Cytoplasmic structures 



Two cytoplasmic bodies were noted by the early observers of 

 mammalian germ cells. These have been variously designated, 

 but to-day they go by the names of idiosome (figs. 1, 25 and 

 26) and chromatoid body (figs. 1, 18 and 20). According to 

 Lenhossek ('98), the idiosome was first described in 1847 by 

 Merkel in the guinea-pig; the chromatoid body by von Brunn in 

 1876. The idiosome was later noted by other observers in 

 different mammals, and now is regularly expected to be found 

 in all. 



A complete recapitulation of the literature on these bodies is 

 unnecessary, but I will outline the views of the chief or more 

 recent workers. The most complete discussion is to be found in 

 Lenhossek ('98) and Duesberg ('08). 



The problems which have arisen in connection with the idio- 

 some are three: its origin, its connection with the centrosomes, 

 and its fate. Lenhossek found it appearing earliest in some 

 spermatogonia, but not well differentiated there, and figures it 

 containing two small bodies that stain more deeply, which he calls 

 the centrosomes. I have not been able to find the idiosome pres- 

 ent in the true spermatogonia. Lenhossek's figure is not of a 

 spermatogonium, as I interpret the cells, but of a young first 

 spermatocyte in the stage which I have indicated by cell-type B. 

 In fact, all of Lenhossek's figures of spermatogonia are of this 

 cell-type B. I have searched both old and young material for 

 some evidence of this body in spermatogonia, but find none. 



