28 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



fused together in the middle line, for each body segment except 

 the last three, -in which the ganglia are fused to a single mass. 

 In the Caprellidea the ganglia of all the abdominal segments are 

 fused together. 



The alimentary canal consists of a straight tube of uniform 

 diameter, except in the anterior portion, where it is dilated to 

 form the stomach. The latter opens anteriorly by a narrow 

 esophagus, which is curved ventrally. The mouth is bounded 

 above and below by the upper and lower lips. The stomach is 

 ovoidal in form and of very complicated structure. As in all 

 the Malacostraca, a gastric mill is present which includes both a 

 grinding and a straining mechanism. The midgut extends from 

 the posterior end of the stomach to the last thoracic segment. 

 Extending forward on the dorsal side of the stomach from the 

 anterior end of the intestine is a so-called pyloric caecum which is 

 single in the Gammaridea but double in the other groups of 

 Amphipoda. Arising likewise from just behind the stomach 

 are the hepato-pancreatic caeca which extend to a considerable 

 distance posteriorly, lateral and ventral to the intestine. Typically 

 there are four of these tubes present, but in Corophium and 

 Siphoncecctes a single pair is present. In addition to these 

 caeca there is also a " rectal gland," of c'aecal form, extending 

 forward and dorsally from, the anterior end of the hind gut. 

 This rectal gland probably corresponds to the Malpighian 

 tubules of insects and functions as an excretory organ, accord- 

 ing to W. B. Spencer (Quar. Jour. Micro. Sci v ser. 2, vol. 25, 

 pp. 183-191, 1885). It is confined in most Gammaridea to the 

 last three abdominal segments. The intestine opens to the ex- 

 terior through the anus which lies just below the telson except 

 in the Photidae, in which the telson is hollow and is traversed by 

 the posterior end of the hind gut. 



The circulatory system consists of a heart, arteries, and 

 lacunae or sinuses. The heart is tubular in form, open at both 

 ends, and situated in the dorsal part of the thorax immediately 

 beneath the integument, and extending as far back as the sixth 

 thoracic segment. On the lateral sides of the organ are three 

 pairs of openings, called ostia, which are oblique slits, guarded 

 by valves which open inward. In the Hyperiidea there are two 

 pairs of ostia usually and in Corophium the number is reduced 



