28 Moll. 
MOLLUSCA. 
The “ flesh ’ 3 of marine Gastropods contains T13-T95 per cent, of 
soluble salts ; Fredericq, CB. med. Wiss. xxiii. p. 430. 
Niemiec (278), in the course of an elaborate anatomical examina¬ 
tion of the suckers of the animal kingdom, describes-those of the fol¬ 
lowing types of Mollusca :—Pterotracluea coroncita has a bell-shaped 
sucker between the two portions of the fin, consisting of an acetabular 
portion proper, and an envelope ; the former contains (1) radial, 
(2) annular, (3) meridional muscles. The first enlarge the cavity of the 
sucker; the second, in the main, contract it, those of the extreme mar¬ 
gin causing its retraction ; while the last group either enlarge the cavity, 
retract the margin, or press it against the surface of attachment, accord¬ 
ing to the point of their insertion. 
In Pneumoclermon mediterraneum the structure of the sucker resembles, 
on the whole, that of Pterotrachcea , but the structure of the peduncle is 
more complicated, and there is a cuticular layer developed upon the 
margin of the suctorial face, which is perforated by the ducts of minute 
glands. The Octopod sucker has been studied chiefly in Argonauta, 
where it is provided with both intrinsic and extrinsic muscles ; the for¬ 
mer consist of (1) a radial system, perpendicular to the epithelium, both 
of the acetabular chamber and the infundibulum ; (2) circular fibres 
situated beneath the epithelium, and forming a sphincter, which sepa¬ 
rates these two cavities ; and (3) a stellate system which sends out meri¬ 
dional fibres towards the sphincter. The extrinsic muscles consist of six 
groups. The author discusses the actions of these muscles, and arrives at 
results which are, in some points, at variance with those of Girod. In 
the groove which runs round the margin of the sucker are certain large 
poiuted cells, with a thickened cuticle, and the epithelium covering the 
interior of the sucker is of the columnar type. 
The suckers of the Deccipoda are illustrated, in the first instance, by 
those of Sepiola rondeleti , which presents for consideration (1) the basal 
part embedded in the arm; (2) the peduncle; (3) the sucker proper. 
The first contains longitudinal, circular, and radial muscles, the two 
former of which are continued into the peduncle. At the point where 
this enters the sucker is a ganglion. The epithelium is covered by a thin 
cuticle, which takes the form of various horny growths :—(1) The ring 
with its marginal teeth ; (2) the rods disposed around the edge of the 
suctorial surface ; (3) the spoon-shaped processes immediately surround¬ 
ing the aperture of the sucker. In the tentacular suckers the muscula¬ 
ture is less powerful than in those of the arms, and the floor forms a thin 
layer, not a solid piston. In the remainder of this section of the paper, 
the different elements of the sucker are treated in succession, and their 
homology and functions pointed out, and the various forms of suckers 
and hooks are shown to be modifications of a common type. 
8 . Digestive System. 
The alimentary canal of Fissurella resembles in general that of Hati- 
otis ; there are, however, only two radular cartilages instead of four; only 
two oesophageal pouches are present, which are of such delicate structure 
