6 



The spleen, a dark, triangular mass attached to the posterior 

 border of the curve of the stomach. 



The spleen of Eugaleus is a long, slender body extending from the middle 

 of the proximal limb of the stomach around the posterior end of that organ 

 and forward again along the distal limb for two-thirds of the length of the 

 latter. 



The pancreas, a firm white mass the larger part of which lies 

 dorsal to the posterior end of the stomach. One extremity lies on 

 the ventral surface of the junction of the stomach and intestine. 



The reproductive glands, (ovaries or testes), lying on either side 

 of the midline dorsal to the anterior portion of the liver; they may 

 be mistaken for small lobes of the liver. 



The reproductive glands of Eugaleus are long bodies lying above the stomach 

 and intestine. They are fused to each other for almost their entire length. 



The kidneys, two long, slender, brownish bodies extending along 

 the dorsal wall of the abdominal cavity outside the peritoneum, on 

 either side of the midline. 



The dogfish usually furnished for dissection are immature, hav- 

 ing the genital glands and ducts only partly developed. In ma- 

 ture females the oviducts are conspicuous tubes ventral to the kid- 

 neys. In young specimens they appear as slender, white tubes ex- 

 tending along the inner borders of the kidneys. Anteriorly, the 

 oviducts pass ventrad over the front of the liver to the ventral wall 

 of the body; at the same time they unite to form a funnel, the 

 ostium tubae, which opens into the coelom. Vestigial oviducts open- 

 ing into the coelom are found in the same position in males. 



In males, the vasa deferentia appear as slender, irregularly 

 coiled white tubules lying near the medial border of the kidneys; 

 they are much less conspicuous than the oviducts, especially in 

 young males. 



THE ALIMENTARY SYSTEM. In dissecting the following organs, 

 care should be taken not to break the connections of the organs with 

 each other or with other parts, or to cut blood vessels. Organs 

 should not be removed until such procedure is directed. 



The mouth and pharynx can be studied to better advantage later 

 with the dissection of portions of the vascular system. 



The oesophagus can be seen above the liver, by pressing that 

 organ aside, as a somewhat constricted tube entering the anterior 

 end of the abdominal cavity. It immediately joins the stomach, 

 which is more or less expanded according to the amount of food 

 contained in it. 



The stomach passes directly back for more than half of the 

 length of the abdominal cavity, then turns abruptly forward, form- 

 ing a distal limb about a third as long as the proximal. (Two- 

 thirds to three-quarters as long in Eugaleus.) The distal limb 

 ends with a sharp turn to the right, where it is constricted by the 

 pyloric sphincter, which marks the end of the stomach. 



The narrow beginning of the intestine forming the turn to the 

 right and backward is frequently distinguished as the duodenum. 

 It leads from the stomach directly into the large intestine, a wide, 

 straight tube marked externally by a spiral line of several turns. 

 The large intestine narrows posteriorly, forming a region some- 

 what arbitrarily termed the rectum, which opens into the cloaca 

 through the anus. 



Dorsal to the rectum and attached to that body is a narrow 

 spindle-shaped body, the rectal or digitiform gland. 



The liver is attached to the anterior wall by a broad base, the 

 peritoneum being reflected over the entire remaining surface. The 



