CALLINECTES HASTATUS. 137 



5. Cut across a gill and notice its afferent and efferent vessels. 

 The latter is continuous with one of the sinuses which empty 

 into the pericardial cavity. Can you determine how many 

 sinuses there are? Do you understand how the heart receives 

 blood? 



Reproductive System. Beginning antero-laterally, on one 

 side, dissect out the reproductive organs, noting at the same time 

 the distribution of arteries. 



(a) Female reproductive organs. Each ovary passes inward 

 and backward, anastomoses with the one of the other side be- 

 hind the stomach, and extends back to the abdomen. On a 

 level with the posterior part of the stomach a branch passes down- 

 ward and outward and is continuous with a dense, white organ, 

 the seminal receptacle. Leave this receptacle in place but remove 

 the entire ovary. 



(6) Male reproductive organs. The slender testis passes 

 inward and backward, anastomoses with its fellow of the other 

 side behind the stomach, and is continued as a thick, much- 

 coiled tube, the vas deferens, to the median side of the flank. It 

 then runs forward nearly to the stomach, turns back again, and 

 enters the substance of the flank. By removing the top of the 

 flank and the upper side of the coxopod of the swimming leg, it 

 can be followed to its external opening, 



Digestive System. (a) The liver fills all of the body-cavity not 

 occupied by other organs. Remove the portion of it that is in the 

 region of, and anterior to, the stomach, noting its connection 

 with the alimentary tract. 



(6) The stomach is a chitinous box divided into a larger car- 

 diac and a smaller pyloric portion. Find the duct from the liver, 

 and a slender, white, coiled tube, the pyloric ccecum. 



(c) Follow the delicate intestine back beneath the heart. 

 Between the posterior edges of the flank is a white mass composed 

 of a coiled tube, the intestinal ccecum. Remove the terga of the 

 abdominal segments, follow this csecum to its connection with 

 the intestine, and follow the latter to the anus, noting its chiti- 

 nous lining. 



