1917] Yocoin: Some Phases of Spermatogenesis hi the Mouse 37:{ 



The latter two stains were used on the slides upon which most of 

 the studies were carried on. Each has its own advantages. The phos- 

 photungstic-acid haematoxylin is a much more satisfactory stain for 

 a study of the spindle fibres and centrosomes, and has the advantage 

 of being a much less opaque stain than the others. It permits a study 

 of the shapes of the chromosomes and aids in the study of the 

 equatorial plate stages as seen in side view. It also has the advantage 

 of staining the cytoplasm, thus doing away with the need of a counter- 

 stain. The haematin is a better stain for the study of the prophases, 

 since it is opaque and causes less confusion of the spireme. 



The optical equipment employed consisted of a Zeiss 2 mm. oil 

 immersion objective and a Zeiss No. 6 compensating ocular; and for 

 higher magnifications, a Holos No. 20 ocular manufactured by W. 

 Watson & Sons, London. 



STRUCTURE OP THE TESTES 



The structure of the mammalian testis is so well known that it 

 needs little description. In the mouse there is little connective tissue 

 binding the tubules together, and when the tough outer membrane is 

 cut the tubules are pushed out as if they had been held imder pressure. 

 In a given section of a testis the tubules are cut at all angles. In those 

 cut longitudinally it is easily seen that the cells along the entire length 

 of the tubule are not in the same condition. 



A cross-section of any tubule shows several of the stages of sperma- 

 togenesis. Next to the basement membrane lie the spei'matogonia and 

 the Sertoli cells, the former often scarce and quite indistinct, appai-- 

 ently crowded out by the foot cells. Soinetimes spermatocytes are 

 next to the membrane, but usually they are separated from the outer 

 edge of the tubule by the spermatogonia. Still farther towards the 

 lumen of the tubule come the spermatids and finally the spermatozoa 

 in various stages of development. 



In the testis of a mouse three weeks old there are no spermatids. 

 The majority of the cells are the primary spermatocytes, and none is 

 older than the young secondary spermatocyte. In most eases the 

 lumen of the tubule has not formed, the cells making a solid cord. 



In a mouse aged five weeks, development has continued so far that 

 many spermatids may be found and even a few spermatozoa; but 

 apparently the latter are not fully matured, l>eing well imbedded in 

 the Sertoli cells. 



