12 



Besides this, the posterior eentrosome becomes elongated to form 

 the axial filament, and the cytoplasm forms the sheaths of the neck 

 and tail. The spiral fihiment of the connecting piece is derived 

 from the cytoplasmic mitochondria. At this time, a large part of 

 the cellular cytoplasm is cast off. Meanwhile, the spermatozoa 

 sink their heads into the long protoplasmic processes of the Sertoli 

 or " nurse " cells which furnish nutritive material for their com- 

 plete development. Finally the adult cells are cast off into the 

 lumen. The structure of the spermatozoa, and a discussion of the 

 semen will be taken up later. 



Epididymis: The epididymis is divided into three parts: the 

 head, body and tail. The head is made up principally of the 

 lobules formed by the much-coiled efferent ductules proceeding 

 from the rete. The ductules, about twelve in number in the bull, 

 unite to form the body, which remains coiled and runs along the 

 postero-medial part of the testicle to which it is more or less closely 

 attached. To quote Ellenberger (23) : " The transition from the 

 rete into the ductules is gradual, as the characteristic epithelium 

 of the latter (ductules) begins in cavities without walls, and at 

 first, gradually form a wall which is well marked out as a thin 



ring of interstitial tissue The epithelium of the ductules is 



in sharp contrast to the rete in that it has a single-layered ciliated 

 columnar epithelium, in which here and there one finds round basal 

 cells. The dark and light columnar cells alternate; the cilia are 

 often cemented together, and form cone-shaped, homogeneous 

 appearing protuberances. The secretorj^ activit}^ is quite clearly 

 observable. In the light cells one finds secretory globules, accumu- 

 lating in rows, sometimes above, other times below, arches of cells. 

 The secretory droplets pass from the cells into the lumen, and 

 often lie in irregular layers on the epithelium ; also the basal cells 

 appear swollen and shoved out between the cylindrical cells." At 

 the lower extremity of the testicle, the tail is formed, which is 

 globular in shape, and more or less loosely attached to the testicle. 

 Here the ductules anastomose freely, gradually become less coiled, 

 and end in the single excretory tube, the vas deferens. The epithe- 

 lium at the tail part is more or less of the pseudo-stratified 

 columnar, ciliated variety. Outside this is a membrana propria, 

 a circular muscular layer, and a connective tissue coat. The secre- 

 tory activity is very marked here and one finds much secretion in 

 the lumen. Courrier (24), working on the bat, suggests that the 

 glandular activity is conditioned by the secretion from the inter- 

 stitial (endocrine) gland. The action of the secretion is to dilute 

 the large mass of spermatozoa present, nourish them to some extent 

 and also stimulate them to active motility. Stigler (25) states 

 that the properties of the sperms are modified in the epididymis; 

 the motility, the ability to resist heat, and other properties are 

 augmented, at least in the case of the guinea pig, rat, and mouse. 

 Some authors state that the sperms first become motile when in 

 contact with the prostatic secretion, but I have repeatedly exam- 



