PALINURUS OR THE SPINY LOBSTER OF BOMBAY. 379 



formed from the stomodccum ; the whole of the abdominal and the 

 greater part of the thoracic gut from the proctodoeum. All the epider- 

 mis we have yet studied in Palinurus both of the outer integument and 

 of the apodemes is covered with a chitinous cuticle. That lining the 

 alimentary canal is no exception, and is even in parts calcified to form 

 stout teeth and plates. 



The stomach is divided into a dilated anterior or cardiac portion 

 and a smaller, posterior, pyloric portion (Gr. pylorus, a gate-keeper 

 or durwan). In man and other Mammals the gullet enters the 

 stomach just after it has passed through the diaphragm in a position 

 quite close to the heart. Hence as anatomy was first studied in the 

 mammals, anatomists came to call the gullet end of the stomach the 

 " cardiac" end. Later the name was continued in this sense in de- 

 scribing any stomach. I need not point out that in Palinurus the 

 " cardiac " end of the stomach is that furthest from the heart. 



The chitinous lining is thick. Its calcified portions are called 

 ossicles. They support three large and two smaller teeth, which by the 

 action of the muscles attached to the ossicles crush and tear the food. 

 The whole apparatus is commonly called the " gastric mill." 



The gizzard and intestine should be removed, emptied of their 

 contents and boiled for a few minutes in a solution of caustic potash or 

 soda. This will remove all muscular and connective tissue, leaving 

 the chitinous structures only. Wash in water and open with scissors 

 along the mid ventral line. 



You will notice externally a pouch on the dorsal surface, between 

 the pyloric and cardiac regions. Two white T shaped calcifications will 

 be seen, the legs of the Ts meeting at the bottom of the pouch. The 

 cross bars of the Ts are placed transversely on the top of the cardiac 

 and pyloric walls of the pouch respectively, they may therefore be call- 

 ed the cardiac and pyloric ossicles. The tail of the anterior larger T is 

 called the urocardiac ossicle (Gr. oura, a tail); of the posterior T, the 

 prepyloric on account of its position. These four pieces are movably 

 articulated with one another. The prepyloric ossicle terminates 

 ventrally in a strong yellow median tooth, which curves round the 

 end of the urocardiac ossicle where these two legs of the Ts articulate. 

 From the outer ends of the transverse cardiac ossicle a pterygocar- 

 diac (Gr. pteryx pterygos, a wing) ossicle runs backwards and down- 

 wards on each side along the margin of the pouch referred to above. 

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