210 A. W. GREENWOOD 



Cytoplasmic Inclusions. 



So far in my description of the spermatogenesis of Phasco- 

 larctus I have made no mention of cytoplasmic structures. 

 Beyond noting their occurrence in the germ cells I have done 

 little to determine their nature. 



In the cytoplasm of the spermatogonia and meiotic stages 

 a large round body is to be seen (PI. 15, fig. 6). This varies 

 greatly in size and staining capacity at different stages. In 

 some stages it is quite deeply stained, notably in the spermato- 

 gonia, leptonema, and early pachynema. Later it stains 

 capriciously, and eventually, during the first meiotic division, 

 becomes quite pale (PI. 15, figs. 12 and 13). It does not divide 

 during the division but passes indiscriminately to one or other 

 of the secondary spermatocytes (PI. 16, fig. 16). It occasionally 

 is found in the early spermatid nuclei, but I have been unable 

 to find it at any later stage. 



This body, I believe, is probably the same as that figured 

 by Gatenby in his work on the ' Cytoplasmic Inclusions of 

 Germ Cells ', as an excretory granule. 



Another cytoplasmic inclusion seen in all stages of spermato- 

 genesis is a very pale, somewhat sausage-shaped body lying 

 close up against the nuclear membrane (PI. 15, figs. 6 and 10). 

 It is towards this body that the synizetic contraction takes 

 place. It is found in all the secondary spermatocytes and 

 spermatids, although I have never found any sign of its division 

 during any of the stages in spermatogenesis. From its behaviour 

 I believe this to be the archoplasmic mass. 



Other cytoplasmic inclusions are the chromatoid bodies. 

 These are conspicuous in the sections fixed with Flemming, 

 but are pale and inconspicuous in those sections fixed in Bouin. 



The leptotene nucleus always contains one or more deeply 

 staining granules. In the pachytene stage also the nucleus often 

 contains a deeply stained granule usually lying close beneath 

 the nuclear membrane (PI. 15, fig. 7). These granules appear 

 to give rise to the chromatoid bodies seen in the cytoplasm of 

 the germ cells at different stages (PI. 16, fig. 28). 



