26 bulletin: museum of compakative zoology. 



and that it may largely or wholly disappear when the stomach is 

 widely distended with food. Its histological structure agrees with 

 that of the stomach. 



In Paranemertes californica the pylorus is extremely short, open- 

 ing into the intestine at a point only about twice as far behind the 

 brain as the distance from the brain to tip of snout. The intestinal 

 caecum is correspondingly reduced to a few pairs of lateral lobes 

 extending forward for a very short distance in front of the jDoste- 

 rior opening of the pylorus. Posterior to the caecum proper the 

 intestine exhibits the same anatomical and histological features as 

 the caecum of related forms, while the intestine proper commences 

 a considerable distance more posteriorly. This condition has evi- 

 dently arisen from a disappearance of the long, slender pylorus of 

 the typical hoplonemertean, so that the pylorus opens near the 

 anterior end of the long caecum, instead of far back as in most 

 other members of the order. 



In Carcinonemertes, which lives on the juices of crabs on which 

 it is parasitic, the intestinal caecum is practically wanting, the stom- 

 ach being closely connected with the proboscis and transforme<l 

 into a barrel-shaped chamber which opens directly into the broad 

 intestine posteriorly. The intestinal lobes are also very much 

 reduced. 



The lining of the mouth, esophagus, stomach, and pylorus origi- 

 nates from the ectoderm of the embryo, while the intestine and 

 intestinal caecum are entodermic in origin. 



C. Bdellonemertea. — ^In Malacobdella the proboscis and 

 esophagus open together into a broad atrium, situated immediately 

 in front of the brain and opening externally at the tip of the snout. 

 The esophagus is large, and is provided with finger-like processes, of 

 which the anterior ones, when fully extended, may be protruded out 

 of the mouth opening, where they are moved to and fro like tactile 

 organs (Takakura, '97, p. 106). The esophagus is constricted 

 before oj^ening into the intestine, which is without lobes or diverti- 

 cula of any sort, but differs from that of all other nemerteans in 

 being strongly convoluted, and much longer than the body. The 

 anus opens dorsally, above the sucking disk with which the posterior 

 end of the body is provided. 



