Open the proximal limb of the stomach by a ventral incision which shall not cut any large blood vessels. Wash out the interior. Observe the three coats of the stomach; the outer peritoneal, the middle muscular, and the inner mucous coats. In the anterior portion of the stomach the mucous coat projects in the form of large papillae (absent in Eugaleus). Posterior to these, observe the irregular folding of the mucous coat, depending upon the degree of contraction of the muscular coat. The muscular coat consists of an outer circular and an inner longitudinal layer of muscle fibres. Separate the two layers from each other and from the mucous coat; observe the network of blood vessels between the longitudinal muscles and the mucosa. Open the pyloric end of the stomach, continuing the cut through the pylorus into the intestine. Examine the coats as before, observing especially that an outer layer of longitudinal muscle fibres is frequently developed, and that the pyloric valve is formed by an increase in the thickness of the coat of circular fibres. Cut through the wall of the large intestine along the right side from its anterior end to the rectum. Do not cut deeper than the thickness of the wall. Corresponding to the external markings, the mucous membrane projects internally in a spiral fold, known as the _spiral valve_. Separate the wall of the intestine from the edge of the spiral fold upon both sides of the longitudinal incision, exposing a considerable surface of the valve. Wash well, and observe the character of the valve, the direction of the folds, and the manner of the reversal of their direction which usually takes place in the posterior half of the valve. Cut across the _rectal gland_ at its middle. Observe the character of its tissues, and then insert a bristle into the central cavity of the gland and pass it into the rectum. Open the rectum and note the point of communication of the two organs. URINARY AND REPRODUCTIVE ORGANS. The _kidneys_ (_mesonephri, Wolffian bodies_), are slender bodies extending along the entire length of the dorsal wall of the abdomen. The posterior moiety of each is thicker and wider than the anterior, which appears to have largely lost the functions of excretion in adult dogfish. Notice the position of the kidneys outside the peritoneum. THE MALE. The _testes_ are white bodies lying to the right and left of the oesophagus, dorsal to the anterior portion of the liver. Each is suspended by a fold of the peritoneum, the _mesorchium_. (The testes of Galeus are long bodies attached to the sides of the mesentery.)