Mr. Jeffreys on the Animal of Stilifer Turtoni. 333 
spawn, which appeared to be in various stages of development. 
The adult Stilifers were not firmly attached to the Echinus (like 
the Caligus to a codfish), but frequently shifted their places by 
creeping between the spines. I gently removed one of them ~ 
with a stiff camel’s-hair brush, and placed it in a glass tube with 
sea-water. It was at first very sluggish or timid, and evidently 
unaccustomed to its new habitat, lyimg at the bottom of the 
tube; but afterwards it recovered itself, and crawled up the 
side by means of the front part of its foot, very slowly and by 
an imperceptible movement ; the other part of the foot was not 
pressed to. the glass, but rested on the mantle. The foot was 
occasionally twisted about and contracted, as if through uneasi- 
ness. The animal was never wholly withdrawn into the shell, 
although I irritated it with that object. The sht in the foot 
probably serves for the admission of water into some tubular 
cavity or vessels which permeate this organ: this would have 
the effect of enlarging and swelling the foot, so as to protect the 
Stilifer from being crushed by the spines of the Kchinus. A slight 
leverage or action of this kind at the base of the spines would, 
of course, answer the purpose far better than a much stronger 
leverage or power exerted at the top of the spines. The fry are 
enveloped in a gelatinous case. When detached and examined 
under a microscope, each had three lobes, of which the two 
larger were in front; these were finely ciliated, the cilia being 
rather long, and their points sometimes touching the surface of 
the glass cell which contained the fry. The fry rapidly whirled 
themselves about by means of the cilia, but occasionally rested. 
They occupied nautiloid shells of a single turn. 
One of the Stilifers appeared to be full of spawn-masses, 
which were perceptible with the microscope by reason of the 
shell being transparent. The other Stilifer was a male. I after- 
wards replaced the latter in its old quarters, where it was evi- 
dently more comfortable than in the glass tube; and it soon 
adhered to the sea-egg by the prehensile lobe of its foot, and 
settled down among the spines. 
The ciliation of the body in Stilifer is also a characteristic 
feature of Homalogyra (perhaps the living representative of 
Euomphalus), which is a minute (but not microscopical) mollusk, 
without tentacles, and forms a discoidal shell. It is an inhabit- 
ant of the European seas, and comprises two species. Forbes and 
Hanley called one of these species Skenea nitidissima, and the 
other Skenea Rota. Dr. Fischer imagined that the first-named 
species was the fry of some larger mollusk, because it was ci- 
hated; but he must have either overlooked the fact, or else not 
have been aware, that im all the species of Zrochus, Rissoa, and 
