A VERY active Mollusc, given here chiefly on account of the opportunity
afforded by the birth of young fry in Mr. Lloyd’s tanks. The _Nassa_
feeds on small animalcules, for which, in aquaria, it may be seen routing
among the sand and stones, sometimes burying itself among them so as only
to show its caudal tube moving along between them. A pair of Nassæ in
Mr. Lloyd’s collection, deposited, on the 5th of April, about fifty
capsules or bags of eggs upon the stems of weeds (fig. 2 _b_); each
capsule contained about a hundred eggs. The capsules opened on the 16th
of May, permitting the escape of rotiferous fry (fig. 2, _c_, _d_, _e_),
not in the slightest degree resembling the parent, but presenting minute
nautilus-shaped transparent shells. These shells rather hang on than
cover the bodies, which have a pair of lobes, around which vibrate minute
cilia in such a manner as to give them an appearance of rotatory motion.
Under a lens they may be seen moving about very actively in various
positions, but always with the look of being moved by rapidly turning
wheels. We should have been glad to witness the next step towards
assuming their ultimate form, but were disappointed, as the embryos died.
Fig. 2 _f_ is the tongue of a Nassa, from a photograph by Dr. Kingsley.