MR. T. H. HUXLEY ON THE xMORPHOLOGY OF THE CEPHALOUS MOLLUSCA. 6T 
its left anterior angle, while its pyloric orifice, very close to this, is at the right ante- 
rior angle. Behind the pyloric orifice the rounded head of the crystalline style pro- 
jects from the aperture of the pyloric sac, y, fig. 16. 
Two wide apertures communicate with the liver, and act as hepatic ducts. 
Several considerable ridges of the gastric membrane rise from the floor of the 
stomach ; the principal one is next to the cardia, and there is a smaller between the 
cardia and pylorus. The aperture of the pyloric sac is surrounded by an elevated 
circular ridge, which is slit towards the pylorus, the left edge of the slit overlapping 
the right. The end of the style projecting from this orifice is opposed by one or two 
cartilaginous plates upon the principal elevation. It is only the end of the style which 
is free ; for the rest of its length (2 or 3 inches) it lies in the pyloric sac (X, fig. 17 ), 
which runs back over the intestine, in the thickness of the left side of the mantle, and 
terminates by a rounded extremity. 
It seems probable that the “crystalline style” is secreted by the pyloric sac, and 
that it acts as a gastric plate, assisting in the comminution of the food, although its 
transparent and delicate texture would not seem to fit it for the performance of any 
very important office of this kind. 
Its resemblance in position and structure to the crystalline style of Solen is suffi- 
ciently remarkable. 
Renal System . — It has been shown that in the Heteropoda and Pteropoda a “ con- 
tractile sac ” exists, placed so as to be bathed by the blood entering the auricle. It 
has been hinted that this is a renal organ, and I now proceed to give the reasons for 
my belief that it is so. 
A hollow sacculated organ, with yellowish glandular parietes, surrounds the base 
of the pulmonary sac in the Pulmonata, and opens by the side of the rectum. The 
secretion of this organ has been shown to contain uric acid*. No contractions have 
been observed in it. 
In Fusus, Cyprcea and other Pectinibranchiata, an aperture, frequently seated upon 
a kind of papilla placed at the posterior and upper part of the branchial chamber, 
leads into a wide cavity, which is in relation above with the pericardium, and on the 
sides with the rectum and generative duct. In its anterior wall a yellow gland is 
frequently attached, which consists of large vascular laminse. I observed no con- 
tractions of either the sac or the yellow gland, but my attention was not at the time 
particularly directed to this point. 
Now I think that this sac, with its vascular gland, is exactly comparable in posi- 
tion to the “ contractile sac” and to the renal organ of Pulmonata, while, on the other 
hand, it closely resembles the serous chambers with their contained venous appen- 
dages, which open into the mantle-chamber of the Cephalopoda. 
The venous appendages of the Cephalopoda, however, have been demonstrated to 
be renal organs by containing secreted uric acid, and they possess the faculty of 
rhythmical contraction d-. 
* H. Meckel, Muller’s Archiv, 1846. f Kolliker, Entwickelungsgeschichte d. Cephalopoden. 
MDCCCLIir. 
K 
