204 Prof. H. James-Clark on the Spongie ciliate 
in the neck (¢) and disappears altogether in the collar (0). In 
its general aspect the body with its collar might be compared 
to a wine-glass with a long stem and a globose pedestal. The 
globose part is the posterior half of the body ; and the stem is 
its neck, or anterior half, which tapers rapidly from the main 
part to one-quarter or one-fifth its diameter, and then gradu- 
ally widens to nearly double that thickness at its front, where 
the collar is set on. The front is truncate, or rises into a low 
cone, upon which the flagellum (jf) is based. The posterior 
half of the body usually fills the bottom of the calyx (c) ; but 
the rest and the neck (7) stand off from it at a very appreciable 
distance. In this respect there is a marked difference between 
this species and S. marina (§ 8). In the latter we might say 
that the body is suspended from the aperture of the urceolus ; 
but in the former it rests on the bottom of the calycle. Not 
unfrequently, however, the whole body of this species lies. 
loosely within its calyx (fig. 37). 
The collar (6) is an excessively hyaline, filmy membrane, 
whose distal margin is so extremely delicate as to almost 
defy detection with the highest powers. In the latter respect 
it is a more difficult object of research than that of S. marina. 
Generally speaking, it may be described as obconical, but with 
greatly varying degrees of width. In this relation it agrees 
perfectly with that of S. marina, and therefore need not be 
redescribed here. At its greatest height it equals that of the 
body, and always terminates in a smooth edge. In plasticity 
it is also equal to that of the marine species. In one instance, 
when the animal was disturbed by a predaceous Rotifer, its 
whole body quickly retracted, and the collar totally disappeared, 
as if melted down with great rapidity, but soon after protruded 
slowly, at first with a broad base (fig. 374, 6), and then rapidly 
narrowed at the latter point and assumed its usual proportions. 
The flagellum (fl) differs from that of S. marina, both in 
proportions and deportment. It is usually rigid, and projects 
considerably beyond the collar when the latter is at its greatest 
height. It has a decided arcuate figure, with a uniform thick- 
ness throughout, excepting near the basé, which tapers rapidly 
from the low cone in the middle of the front. Its apex moves 
with quite gentle spasmodic twitches, and the whole becomes 
flexible (fig. 37>, /) when feces are ejected or some unde- 
sirable particle enters the area within the collar. 
The mouth was not actually seen; but that it exists some- 
where about the base of the flagellum was sufficiently demon- 
strated by minute particles of food being seen thrown by the lat- 
ter organ against the front, and rapidly disappearing there. The 
anus (fig. 37, a) certainly opens within the same area, as parti- 
