134 KANSAS UNIVERSITY SCIENCE BULLETIN. 



In the first of these counts the sections are thick enough 

 so that one Sertoli cell would not be in more than two sections, 

 but the numbers of groups of 1, 2, and 3 spermatozoa far 

 surpassed the numbers of groups of 9, 10, and 11. From this 

 it seems that the number can not always be as high as twelve, 

 and seldom, if ever, higher. In the 8-micra sections, it would 

 be possible for a Sertoli cell to be in three sections, and this 

 would account for a larger number of small groups of sper- 

 matozoa, but hardly for as great a difference as there is. In 

 both counts the numbers of groups of 5, 6, and 7, are far in ex- 

 cess of other numbers. 



Short pieces of unstained tubules were teased and stained. 

 Some pieces of tubules were stained in alum cochineal, or 

 Delafield's hematoxylin, cleared in cresote and then teased or 

 cut longitudinally and spread out. One difficulty here is being 

 unable to determine the stage of development of the sper- 

 matozoa. It is quite seldom, too, that the Sertoli cells are 

 sufficiently isolated to enable one to make counts of their con- 

 tents. No counts were recorded, but in those cells which seem 

 to be complete there are more often 8, 9, or 10 spermatozoa 

 than 11 or 12. 



Finally, sections 20, 25, 30, 35, and 40 micra thick were pre- 

 pared and stained with iron hematoxylin with or without 

 eosin, and with tricolor. The tricolor did not give as good 

 results, though less destaining would probably have improved 

 it. With iron hematoxylin, the spermatogonia, spermatocytes 

 and spermatids are all a light brown, and the spermatozoa a 

 dead black when mature. Thus especially with an immersion 

 oil objective, the spermatozoa are clear and distinct. In the 

 20-micra sections a few Sertoli cells can be found, the sper- 

 matozoa of which are invisible at both the upper and lower 

 plane of the section. In sections 30 micra thick a Sertoli cell 

 with 7 or 8 spermatozoa may be in focus at the upper level of 

 the section, may disappear, and at the lower level another ceil 

 immediately beneath the first and equally well filled may come 

 into focus. In 40-micra sections a third cell may sometimes be 

 seen directly above two others. Thus there can be no doubt 

 but what complete cells are contained in these sections. 



In all counts care was taken to have the complete thickness 

 of the cell, and in practically all the ent're length could also 

 be traced. Counts were made in several stages. The clearest 

 and easiest were those made when the spermatozoa were ap- 

 proaching and at the base of the cell, or at the base and begin- 



