72 M. Coste on Fresh-water Polypi. 
coming the closure occasioned by the contraction of the sphine- 
ter of the sheath to which they are antagonists. The Paludi- 
cella present, in this respect, a difference which it would be 
tedious to explain, but which will be accurately represented 
in the plates. 6¢h, Of the regulator muscles of the sheath, to 
the number of about ten. They are arranged like so many 
cords, which, from the anterior third of the length of the in- 
side of the cell into which they are inserted, extend in the form 
of rays, converging forward from behind towards the circum- 
ference of the posterior extremity of the sheath, to the points 
of whose circumference they attach themselves. Their use 
seems to be to enable the sheath to maintain, in a permanent 
manner, the infolded arrangement which is natural to it, and 
likewise to oppose any undue unfolding of the animal. On 
this account, we designate them the regulators of the sheath. 
They are much fewer in the Paludicella than in the horse-shoe 
plumed polypi (& panache en fer a cheval). The dilating and 
regulating muscles of the sheath are the only portions which 
have any traces, however obscure they may be, of the radiatory 
arrangement of the fresh-water polypi; all the rest of the or- 
ganization being evidently binary. 
The Digestive Apparatus, which is composed of three very 
distinct compartments, the cesophagus, stomach, and rectum. 
The cesophagus commences in front by a circular and ciliated 
mouth, surmounted by a tongue which is also ciliated, which 
Serves as an operculum, and varies in form, size, and arrange- 
ment, according to the species. It communicates behind with 
the stomach, by a mouth shaped as in the tench, projecting into 
the interior of this organ. This tongue and tench-like mouth 
form an anatomical arrangement which belongs exclusively to 
the horse-shoe plumed polypi, being absent in the Paludicella, 
which, in this respect, present an entirely different conforma- 
tion, and in which it is also found that the absence of a tongue 
and of the tench-shaped mouth coincides with that of a palmed 
membrane, which unites the base of the tentacula of the polypi 
to the horse-shoe plume. The stomach forms a large pouch, 
terminated posteriorly in a cul-de-sac, and presents through- 
out the extent of its inner surface many projecting longitudi- 
