washed for a few hours in flowing water, embedded in paraffin, 

 sectioned, fixed to cover glasses, stained in Heidenhain's iron-lack- 

 haematoxylin, counter-stained in a saturated aqueous solution of 

 acid fuchsin, washed, dehydrated, and cleared in oil of bergamot 

 and xylol. Mount on balsam. 



Study under high power. On moving the section 

 about you will observe that the variously cut seminiferous 

 tubules show different stages of development. Within the 

 tunica propria of a resting tubule are seen several layers of 

 cells, in the outermost of which are found the spermat- 

 gones (parent cells), and the lower portion of the support- 

 ing cells of Sertoli. Then comes a layer of quite large 

 cells, the spermatocytes (mother cells), descendants of the 

 spermatogones. Lining the lumen of the tubules are found 

 several layers of small cells, the spermatoblasts (daughter 

 cells). The mother cells dividing by indirect cell division 

 give rise to the small inner cells; from these the sperma- 

 tozoa are developed. Search for a tubule showing the 

 fusion of the spermatoblasts with the supporting cells of 

 Sertoli. Other tubules will show the successive steps in 

 the development of the spermatozoa in these cells until 

 they are found free in the lumen of the tubule. Observe 

 especially the change undergone by the accessory nucleus 

 during the development of the spermatoblasts into the sper- 

 matozoa. In the spermatoblast the accessory nucleus is 

 seen as a relative large ball stained black in this prepara- 

 tion ; it is situated on one side of the nucleus. As develop- 

 ment begins the accessory nucleus becomes demilunar in 

 shape and applies itself to the nucleus. It then assumes a 

 triangular shape, and finally becomes the head cap of the 

 fully developed spermatozoa. Sketch portions of 3 or 4 

 tubules showing the several stages of spermatogenesis, as 

 seen under high power. 



(c) Ovary. 



The ovary of a rabbit or cat was hardened in mercuric chloride, 

 stained in Delafield's hsematoxylin, embedded in paraffin, and 

 sectioned. Fix and mount in balsam. 



Study first under low power. The ovary is covered by 

 a single layer of germinal epithelium. It consists of a 

 medullary portion, in which large vessels are found, sur- 



