24 
Fridtjof Nansen. 
[No. 7. 
together (vide fig. 7, t *). These capsules are filled with small cells 
or spermatozoa; exteriorly, they are surrounded by a connective- 
tissue envelope which is a direct continuation of the connective- 
tissue of the mesorchium. Among the cells filling the capsules, it 
is, in well prepared sections of the testes, very easy to distinguish 
two kinds, viz. epithelial cells forming a folicular epithelium 
investing the inner side of the connective-tissue envelope of the 
capsule, and the real sexual cells which after subdivision are 
converted into spermatozoa. 
The folicular epithelium is very prominent, especially 
in young capsules (vide fig. 12, f, e); it forms, here, a distinct 
continuous layer on the inner side of the connective-tissue envelope, 
and consists of square or cubical cells with distinct ovoid or spherical 
nuclei. These nuclei are, in young testicular capsules (where the 
sexual cells are very large, cf. infra), much smaller than the nuclei 
of the sexual cells (spermatogons and spermatocy tes) ; they have a 
distinct and prominent membrane, a not very granular (generally 
rather clear) contents, in which one, or sometimes a few nucleoli 
usually are observed; there is, as a rule, no indication of an 
extraordinary activity, or of divisions, to be traced in those nuclei. 
In the testicular capsules approaching the mature state, and 
containing swimming spermatides or spermatosomes (cf. infra), the 
folicular epithelium is very often rather difficult to trace. It forms 
there, as a rule, a flat epithelium. In sections of such capsules, 
oblong epithelial nuclei with surrounding protoplasm occur, more 
or less sparingly, along the inner surface of the thin connective- 
tissue envelope enclosing the capsule (vide fig. 11, fe). That these 
nuclei belong to the original folicular epithelium of the young 
testicular capsules, may easily be seen on examination of capsules 
in the transition-stages of maturity. The epithelium remains as a 
rather thick continuous layer, through a great many stages of the 
capsules, but when the formation of the spermatides begins, and 
during the later stages of the spermatocytes ; when the capsules are 
enlarged so much that the sexual cells begin to be separated from 
each other, and to swim isolated in the fluid filling the capsule; 
the folicular epithelium is gradually flattened and the nuclei be- 
*) These capsules are, as a rule, situated much closer together than the 
ovarir.n capsules, and are not, generally, as Cunningham has represented in one of 
his figures of a transverse section of a male organ (loe. cit. Pl. VI, fig. 8). His 
fig. io is more like the ordinary state. 
