812 Proceedings of the Royal Society 
most part differentiated into spermatozoids, though a few degenerate 
into a problematic body. 
The researches of Jensen, to which 'we have already referred, 
extended also to Vertebrates. Within the ampullae of Plagiostome 
fishes two forms of cells occur (a) with large round nuclei — the 
future spermatogonia, ( b ) with narrow smaller nuclei — the follicular 
cells. It is important to note, however, that he maintains that the 
latter also develop into the former. From the division of each 
spermatogonium a cellular pillar results — a spermatogemma of sper- 
matocytes ; while a single narrow follicular nucleus lies at the base 
of each pillar, forming the Deckzelle of Semper, the Cystenkern of 
Von la Valette, the Hoyau basilaire of Herrmann. The spermato- 
gemmse become eventually, however, hollowed out, and that by the 
destruction of some of the internal spermatocytes, so that the final 
result is that of a number of spermatocytes surrounding a central 
cavity, while the cytophoral portion at the base, towards which the 
sperms dive down, has a distinctly follicular origin. 
The researches of Swaen and Masquelin (1883) on Elasmobranchs, 
Amphibians, and Mammals are of importance, as tending towards 
reconciliation. In the testes of Selachians, when the primitive 
ampullae are once formed, “ male ovules ” (spermatogonia) and fol- 
licular cells, are quite distinct, and the latter do not transform into 
the former. The male ovules divide indirectly to form spermato- 
gemmae, while the follicular cells, after having formed incomplete 
envelopes to the male ovules, and to the spermatogemmae, disappear 
save one, which travels down and insinuates itself between the 
ampulla and the spermatogemma, there constituting the basilar cell. 
The fully-developed spermatogemma of about sixty spermatocytes 
exhibits a central cavity or “ loge caudale,” in which the incipient 
spermatozoa or nematoblasts are embraced, their tails projecting 
into the lumen of the duct. The basilar cell, which has also been 
enlarging, has likewise an influence on their arrangement ; its proto- 
plasm fuses with the intercellular substance of the spermatogemma, 
surrounds the heads and bodies of the nematoblasts, which thus sink 
down towards the basilar nucleus, only to he again expelled by the 
elongation of the latter. A similar process occurs in the spermato- 
genesis of the salamander, where, however, the follicular cells form 
a complete envelope round the male ovules during their whole 
