HAGUE: SPERMATOZOA AND SERTOLI CELLS. 137 



None of the mature Sertoli cells of the rat testes show either 

 rods or rodlets. About the periphery of a section preserved in 

 Flemming's fluid and stained with iron hematoxylin, there are 

 occasional dark streaks on the Sertoli nuclei, which at first ap- 

 peared to be rods. These are not visible in the lighter cells 

 of the central part of the section. The nuclei are uniformly 

 slightly granular and contain a large nucleolus and two or 

 three smaller chromatic bodies, one always close to or attached 

 to the nucleolus. 



In the human testis by far the greater part of the cells seen 

 were primary spermatocytes in various stages, but none divid- 

 ing. At the periphery there were also a few cells in earlier 

 stages, and at the lumen some spermatids and spermatozoa. 

 Some sections of tubules of the rat testis show a row of de- 

 veloping primary spermatocytes at the periphery, then second- 

 ary spermatocytes, between the long Sertoli cells which contain 

 mature spermatozoa. Other tubules show the primary sper- 

 matocytes almost mature, secondary spermatocytes, and Sertoli 

 cells with spermatozoa, pulling away from the wall of the 

 tubule and passing toward the lumen. At the same time there 

 can be seen in other tubules a row of the large primary sper- 

 matocytes inclosing a mass of secondary spermatocytes, which 

 in turn enclose the last of the escaping spermatozoa. The sec- 

 ondary spermatocytes divide quickly into spermatids and then 

 first begin to form in groups. When they are seen elongated 

 and in definite groups about the inner ends of the Sertoli cells, 

 which have grown inward, the mature primary spermatocytes 

 are dividing and the next generation is beginning to appear. 

 The spermatozoa begin to form at the periphery of the lumen, 

 but as they condense more and as the secondary spermatocytes 

 which are being formed, push inward, the spermatozoa make 

 their way toward the base of the Sertoli cell, often clustering 

 close about the nucleus. Even when passing out the nucleus is 

 frequently very close to the spermatozoa. 



Montgomery in speaking of ultimate spermatogonia one 

 quarter of which, he says, contain rods and three quarters lack 

 rods, says : "The ratio is somewhat less than 1 to 3, which is 

 readily explained on the ground that some of the spermatogonia 

 with rods had already become Sertoli cells and therefore were 

 not included in the count." It would seem, then, that Sertoli cells 

 develop from the ultimate spermatogonia! condition before the 



