46 W. Stimpson on the so-called Melanians of N. America. 
In view of these remarkable characters of the sexual system, 
to packs the propriety of dividing the Tzenioglossate Cteno- 
branchiata into two groups, found it. 
The only family of Ctenobranchiates in which the absence 
of a male organ has previously been known to occur, is that of 
the Vermetidz, which have been recently made the subject of 
an anatomical investigation by Lucaze-Duthiers. As thes 
sessile animals, each individual being glued to its place upon 
some foreign body, and therefore unable to seek out a mate, an 
intromittent organ would be entirely useless to the male. Cuvier, 
reasoning @ priori, deduced from this fact of their sessile habits 
the view entertained by him, namely, that they must have the 
ower of self-impregnation; and he consequently separated them 
m the Ctenobranchiata as a distinct order, under the name of 
Tubulibranchiata. But the circumstance of sessile life is im 
reality not inconsistent with separation of the sexes. There is 
no difficulty in conceiving that the impregnation may take place 
- in the way which is known to occur in the Lamellibranchiata, 
_ the spermatic particles reaching the ovary of the female throug! 
the medium of the water, into which they are discharged by the 
ale. In our freely-moving Melanians, however, such a mode 
of impregnation is quite unnecessary; it is far more probable 
: : * Verg. Anat. der wirbellosen Thiere, 1848. 
