REMARKABLE SPECIES OF ECHIUllOIDS. 51 



The œsophagus (o?s.)'^ is a somewhat narrower tube, measuring 

 25-30 cm. in loniith. Making turns backwards and forwards, it 



Oct ' 



describes narrow 8-likc curves. The inner surface of the œso- 

 jiliagus is distinguished by the presence of closely set, villi-like 

 jirotuberances, which look very much like those in the crop of 

 Th. tœnioides. 



The intestine [in.) forms by far the largest part of the entire 

 alimentary tract. It may be about 170 cm. long when stretched 

 out straight, and is somewhat wider than the œsophagus, measur- 

 ing on an average 8 nmi. in width in the empty state. The transi- 

 tion of the oesophagus into the intestine is externally marked by 

 the point of origin of the collateral intestine {c.i.). At first the 

 intestine, as it starts from the last end of tbe oesophagus, is 

 directed forwards in the anterior parts of the body on the left 

 side. It then crosses over to the right side, above and across the 

 pharynx. Thenceforth it runs posteriorly, pursuing an irregularly 

 tortuous course, down to a point within a short distance from 

 the posterior body end. Here it makes a sharp bend to continue 

 its irregular winding course this time forwards. Coming up to 

 a position in front of the first beginning of the intestine, it makes 

 a second crossing over from left to right above the oesophagus. 

 After that, it starts on the final, posteriorly directed, irregular 

 course, which brinies it to the terminall v situated anus. 



The collateral intestine [c.i.) is a moderately wide tube, 

 running along the anterior parts of the intestine for a length of 

 about 80 cm. The posterior parts of same, unaccompanied by the 

 organ just mentioned, exhibit the siphonal groove (s.f/.), which 

 terminates behind in front of the rectum. This is about 1 cm. 



1) In fig. 49, tlic first part of the rosopluigns was iiiadvcrlenlly siipplii-d witli tlic 

 reference scj., which should he vs. iiLstcad. 



