Chap, xxxi.] THE MALE GENITAL ORGANS. 247 



imposed over one another. The lumen is in all tubes 

 distinct and relatively large. The lining epithelium, 

 or the seminal cells, differ in the adult in different 

 tubules, and even in different parts of the same tubule, 

 being dependent on the state of secretion. 



324. Before puberty all tubules are uniform in 

 this respect, being lined with two or three layers of 

 polyhedral epithelial cells, each with a spherical 

 nucleus. After puberty, however, the following 

 different types can be distinguished : 



(a) Tubules or parts of tubules similar to those 

 of the young state viz., several layers of polyhedral 

 epithelial cells lining the membrana propria. These 

 are considered as (a) the outer and (6) the inner 

 seminal cells. The former are next to the membrana 

 propria; they are polyhedral in shape, transparent, 

 and the nucleus of some of them is in the process 

 of karyokinesis or indirect division (see par. 8) ; 

 others include an oval transparent nucleus. The 

 inner seminal cells generally form two or three layers, 

 and are more loosely connected with one another than 

 the outer seminal cells, and therefore possess a more 

 rounded appearance. Between these a nucleated reti- 

 culum of fine fibres is sometimes noticed, the germ 

 reticulum of von Ebner. But this is merely a support- 

 ing tissue, and has nothing to do with the germina- 

 tion of the cells or the spermatozoa (Merkel). The 

 inner seminal cells show very abundantly the process 

 of indirect division or karyokinesis, almost all being 

 seen in one or other phase of it. 



325. In consequence of this, numerous small 

 spherical daughter-cells are formed ; these lie nearest 

 the lumen, and are very loosely connected with one 

 another. It is these which are transformed into sper- 

 matozoa, and hence are appropriately called spermato- 

 Uasts (Fig. 137). 



Amongst the seminal cells, especially of cat and 



