HOMARUS AMERICANUS MILNE-EDWARDS 131 



ground sufficiently fine pass again to the cardiac sac and are 

 finally vomited. 



The intestine or midgut is a thin straight tube running as 

 far back as the beginning of the sixth abdominal somite. Here 

 it forms a median dorsal blind sac or caecum. The ccecum marks 

 the end of the midgut. The portion of the alimentary canal 

 behind it is the hindgut or rectum. The anus opens ventrally 

 on the last somite. Connected with the intestine is a large 

 digestive gland, often called liver. It opens into the intestine by 



FIG. 29. Circulatory system of the European Lobster after Gegenbaur. 

 From Claus-Grobben, Lehrbuch der Zoologie. C, heart; PC, pericard; 

 Ac, aorta cephalica; A. ab, aorta abdominalis; ,4s, ventral artery. 



means of two short ducts between the pyloric valves. Food is 

 passed into the digestive gland for final digestion. 



Excretory system. The excretory system of the lobster 

 consists of two antennal or green glands which are in reality 

 modified nephridia. They are more or less lentil-shaped bodies 

 situated in front of the stomach. Each gland consists of a blind 

 sac which represents a modified nephrostome, a convoluted 

 glandular tube, a bladder and a short duct. The latter opens on a 

 papilla situated on the coxopodite of the second antennae. 



Circulatory system. The circulatory system of the 

 lobster, although highly developed, is an open system, inasmuch 

 as the arteries and veins open into a system of lacunae and 



