CRUSTACEA, 43 



remove, by means of a dissecting-knife or a pair of 

 scissors, the dorsal portion of the carapace, and of each 

 abdominal segment, observing, as they do so, the red 

 skin which covers the body and forms the shell above 

 it. The powerful muscles of the abdomen lie beneath 

 the red skin, extending upward on either side of the 

 cephalothorax. Some time may be spent in examining 

 the different muscles, and in determining how they act. 

 They should then be removed sufficiently to expose the 

 blood-vessels. The heart is a spongy mass, surrounded 

 by a sac, and situated in a hollow space or chamber 

 formed in the posterior part of the cephalothorax. 

 Jt lies immediately under the skin, and may be dis- 

 tinguished from the other organs by its color. Five 

 arteries are given off from the heart anteriorly; the 

 middle one passes to the eyes, the next partly to the 

 antennae, the succeeding two to the stomach and liver. 

 Posteriorly, one artery arises \ this branches into two, 

 one of which extends through the abdomen, above the 

 intestine, while the other bends down and connects 

 with the sternal artery which runs along the floor of 

 the body, and cannot be traced till the digestive organs 

 and muscles have been removed. On taking out the 

 heart the pupils must cut the sternal artery : they are 

 then ready to study the digestive organs. A probe 

 may be passed from the mouth into the stomach, which 

 is an extremely interesting organ to examine. It is 

 divided into two parts ; the larger or cardiac portion is 

 a sort of mill, where the food is ground by an appa- 

 ratus familiarly known as "the lady of the lobster." 

 The smaller division, or pylorus, is a gate-keeper in 

 the form of a strainer, which will not permit a single 



