84 Invertebrate Zoology. 



the posterior part of the carapace does belong is somewhat 

 doubtful. 



Internal Anatomy. With a strong pair of shears care- 

 fully remove the calcareous shell from the dorsal half of the 

 body, from the rostrum to the telson, noting the points 

 where the muscles are attached. Have the attachments in 

 any way affected the even contour of the exoskeleton? 

 Examine still further the internal face of the removed por- 

 tion of the carapace and see if there is anything to show that 

 there are represented in it certain segments posterior to the 

 groove. 



Remove the dorsally lying pigmented integument, and 

 also the superficial muscles, exposing the viscera. Note 

 the large, anteriorly lying horny stomach. It is held in 

 place by certain gastric muscles. Just back of the depres- 

 sion in the carapace formed by the groove, the heart will be 

 seen. In outline it is somewhat shield-shaped, three angles 

 being directed anteriorly and a single rounded angle project- 

 ing posteriorly. Two small, oblique openings will be noticed 

 on its dorsal side, near the median line. 



Do you find the elongated sexual glands extending on 

 either side from near the lateral angles of the stomach to 

 about the middle of the abdomen? Is the right gland in 

 communication with the left ? If the specimen is a female, 

 the eggs may be seen through the transparent ovarian 

 walls. Examine the outer border of the organ and find 

 ducts leading ventrally. 



Can you follow a blood-vessel, the superior abdominal 

 artery, leading posteriorly from the heart and extending to 

 the telson ? Immediately below, and somewhat covered by 

 the sexual organs, is the intestine. 



