MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 161 



the other, fornihig a very thick wall upon the dorsal and ventral sides of the stomach. The 

 posterior wall of the stomach is thin, like the anterior. Within the inuscuhir la.ver is a white 

 layer of what seems to be elastic tissue, at least as thick everywhere as the nrascle layer. Under 

 the thickest part of the muscular layer, i. e., between the tendons of the stomach dorsally and 

 ventrally, the elastic tissue layer is so thickened as to form thick pads which project into the 

 cavity of the stomach. {Fig. 32.) Except upon the anterior and posterior walls, the inner surface 

 of the stomach is thrown into fine, parallel, longitudinal ridges. Inside the walls of the stomach, 

 covering only the ridged portions, is a thick, chitinous lining, which in life must lie closely upon 

 the epithelium of the stomach and be formed by it, since it copies accurately all the ridges and 

 folds of the walls of the stomach. In my preserved specimens the lining has always been 

 entirely free from the walls, probably as the result of shrinkage. Compared with external chi- 

 tinous parts this lining is quite soft, but nevertheless it must be a great protection to the fleshy 

 walls of the stomach while the food, often mixed with hard, sharp pieces of shell, is being 

 triturated. 



From the anterior edge of the rigid pad of the ventral side of the stomach springs a row of 

 small, slender tentacles. (Fig. 32, T.) I have found fine processes upon the corresponding part 

 of the chitinous lining, which may possibly lie upon and protect the tentacles. What the func- 

 tion of these tentacles can be is hard to imagine. Perhaps they are sensory and have something 

 to do with the passage of the food into or out of the stomach. In view of the character of the 

 deliris found in the intestine it does not seem probable that they are used to sift out the finely 

 divided particles of food. Besides extremely small particles of food one finds in the intestine 

 large pieces of crustacean shells and even entire pleopods. A priori, any sifting apparatus 

 would therefore seem superfluous. It is unfortunate that the condition of my material prevents 

 anv histological examination of these organs. 



The position of these tentacles clearly marks a line of separation between the anterior portion 

 of the stomach into which the cesophagus and intestine open and the posterior portion where the 

 food is ground, and makes the term vestibule seem reasonable in speaking of this portion. (Fig. 



32, V.) 



The opening into the intestine is upon the right side of the vestibule. I have been unable 

 to find the valve guarding the entrance to the intestine mentioned by Owen. From the vestibule 

 the intestine passes to the right around the back of the ccecum and then forward upon the right 

 side of the latter organ. (Fig. 27. I'.) Then, bending downward and backward around the part 

 of the liver connecting the right and left lobes, the intestine forms a backwardly directed loop. 

 (Fig. 27. r and P.) The two legs of the loop lie parallel and close to one another, connected by 

 a delicate mesentery in which runs an artery giving oft' branches to each part of the intestine. 

 (Fig. 27, lA.) The second loop of the intestine is directed upward as well as backward, so that 

 its end lies beneath the siphuncle. A ligament from the right anterior face of the gonad extends 

 to the left leg of the loop and slings the loop of the intestine in position. (Fig. 27, IL; Fig. 38, 1. 1.) 

 The left and larger leg of the loop runs straight forward under the stomach, crop, and liver in 

 the mesentery above the heart and between the anterior renal sacs to the plicated anus upon the 

 inner side of the mantle. The last part of the intestine is thickened and folded longitudinally 

 and is called the rectum. 



The ccecum is a blind sac opening into the intestine 10 to 12 millimeters from its origin 

 and lying ^rithin the first loop of the intestine. (Fig. 27, Coe.) In and about the cojcum 

 is the most complicated part oi the entire digestive tract. The ccecum itself is a thin walled, 

 oval, laterally flattened organ. 18 millimeters in length and 11 millimeters in width. The duct 

 of the liver enters the ciecum opposite the intestinal opening; usually the minor duets of the 

 separate lobes of the liver unite into a common duct before entering the ccecum, but they 

 may open separately. (Fig. 32, HD.) The intestinal and hepatic openings are both near 

 the lower side of the crecum. From the dorsal and posterior walls transverse, shelf-like 

 lamellse extend into the cavity of the ccecum. leaving its lower portion only unobstructed. 

 The surfaces of the lamella? are folded and pitted, so that their appearance lends suppoit to the 

 a priori judgment from their position that the lamelUe must be glandular, adding their secretion 



