586 



EVOLUTION OF ANIMALS 



Part V 



PYLORIC STOMACH- 



INTESTINE. 



ChlTlNOUS LINING 



CASTROUTH 

 GASTRIC EPITHELIUM 



ESOPHAGUS 



•CARDIAC STOMACH 



Fig. 29.14. Upper, A, the sudden increase in size of a lobster after molting. The 

 skeleton that was shed has a crack in the thorax through which the lobster emerged. 

 B, the "soft-shelled" lobster after the molt. The sudden increase in size is due to 

 growth before molting and expansion afterward. Lower, diagram of the stomach 

 of the crayfish with a part cut away to show the gastrolith in the wall of the cardiac 

 chamber. For some time before molting calcium from the old exoskeleton is 

 absorbed by the blood and is stored in the gastrolith. (Upper, after Herrick. 

 Courtesy, Wolcott: Animal Biology, ed. 3. New York, McGraw-Hill Book Co., 

 1946. Lower, courtesy. Turner: General Endocrinology , ed. 2. Philadelphia, W. B. 

 Saunders Co., 1955.) 



in others they lie close to the brain. It is possible to remove the glands from 

 the eye stalks of a crayfish without injuring other structures, and when this is 

 done the animals form gastroliths, absorb extra water, consume more food and 

 oxygen and molt repeatedly. This can be prevented, however, by grafting sinus 

 glands of other crayfishes into those whose own glands have been removed. 

 Other Effects of Hormones. The sinus glands of crayfishes in some 



