the same general form and position as the testes in the male, (d) 

 Oviducts. These are short and go directly down from the ovary to 

 the openings on the third, or middle, ambulatory appendages. 



Make a drawing of your dissection, showing all these organs in 

 place. 



III. DIGESTIVE TRACT. 



(a) Carefully remove the anterior part of the carapace and 

 notice the very large sac-like stomach anterior to the heart. Pass a 

 probe into it through the mouth and short oesophagus, (b) Dis- 

 sect away the exoskeleton and muscles and follow the intestine from 

 the stomach to the anus. Immediately posterior to the stomach is the 

 "mid gut" having a short dorsal diverticulum on it. ( The remainder 

 of the intestine is short and simple.) (c) The digestive gland (the 

 so-called "liver") forms a yellow mass opening by a duct on each 

 side of the mid gut. Wash away its contents if the duct cannot 

 otherwise be found, (d) Remove the intestine and cut open the 

 stomach along one side (under water) and note a large round 

 (cardiac), and a narrow posterior (pyloric) portion. The chitinous 

 lining forms in the cardiac portion three conspicuous tooth-like 

 thickenings. In the pyloric region ridges, set with hairs, reduce the 

 lumen of the stomach to a narrow slit. 



Draw a side view of the digestive tract. 



IV. XERVOUS SYSTEM. 



Remove the muscles of the abdomen until the nerve cord is seen 

 along the ventral wall of the body, (a) Note the relation of the 

 ganglionic swellings to the somites. (b) Follow the cord into 

 the thorax; here it enters a canal, the roof of which must be 

 broken off bit by bit with forceps to show the nerve cord. Note the 

 number of ganglia in the thorax, (c) The cord divides at the 

 oesophagus into a right and left half which meet again at the brain. 

 The brain, or supraoesophageal ganglion, lies just posterior to the eye 

 stalks, close to the exoskeleton, and sends a large nerve into each 

 of the eye stalks. 



Make a drawing of the nervous system. 



XII. VENUS MERCENARIA. (A Pelecypod Mollusk). 



I. PHYSIOLOGY. 



If living speciments are available, allow powdered carmine to settle 

 slowly past the openings of the siphons and determine the direction 

 of the current of water for each. Observe if possible the method of 



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