820 MR. F. E. BKDDARD ON [NoV. 3, 



is simply an exaggeration of the structure of the oesophagus, which 

 is traversed by numerous longitudinal folds. 



The oesophagus passes gradually into the intestine, which is distin- 

 guished by its greater calibre, and extends to the anus without 

 any variation in its character. The intestinal epithelium is ciliated, 

 and the ciliation is continued forwards into the oesophagus as far as 

 the caleiferous glands ; in front of the calciferous glands the 

 oesophagus does not appear to be ciliated. 



The intestine is unprovided with caeca or with glands of any 

 description. 



Tlie txjpldosole has a characteristic form, and serves to distinguish 

 A. multiporus on the one hand from A. novce zelandicp, and A. dis- 

 similis on the other. In the two latter species the typhlosole, on a 

 superficial inspection of the intestine, appeared to be absent ; in 

 transverse sections it may be seen to be present, though extremely 

 rudimentary. On the upper side of the intestine, just below the 

 dorsal blood-vessel, the muscular coat is prolonged downwards for a 

 short distance into the lumen of the gut, and the lining epithelium 

 covers the projection, which only measures -^o of the lumen of the 

 intestine ; in certain regions the typhlosole was a little more com- 

 plicated, being bifurcate at its extremity, indicating an approach to 

 the structure of the typhlosole of A. nmltiporus. 



In this species, on the dorsal side of the intestine, and projecting 

 into its lumen, is a very conspicuous typhlosole. The typhlosole 

 is well developed throughout the greater part of the intestine, but 

 gradually decreases, and finally disappears in the hindermost region 

 of the gut. In the largest example of this species, measuring 

 about 1 1 inches in length, the region of the intestine devoid of 

 typhlosole was rather more than one inch in length. The typhlosole 

 projects into the lumen of the intestine in the middle of the body, 

 where it is well developed, for a space of about half of its diameter ; 

 more exact measurements show that the extreme length of the 

 typhlosole is to the circumference of the intestine as 6 : 30. In 

 transverse sections it nsay be seen that the typhlosole is not a 

 single fold ; it consists in fact of three folds, two lateral and one 

 median, which unite together to form a single fold attached to the 

 wall of the gut. Q^he lateral folds are subequal, and considerably 

 deeper than the median fold ; their vertical diameter is from two to 

 three times that of the median fold. The typhlosole arises from 

 the dorsal wall of the gut at a point exactly between the two dorsal 

 vessels. Its structure is exhibited in Plate LIII. fig. 1. It is an 

 outgrowth of the epithelial wall of the intestine, surrounding a blood- 

 sinus. The cells are tall and columnar, and resemble in every par- 

 ticular the lining epithelium of the intestine. Between the cells 

 which form the opposite walls of each of the three folds is a con- 

 tinuous blood-sinus, whicli widens out at the caecal extremity of 

 both the median and the lateral folds, and also above the point of 

 junction of the three folds, where it forms a wide reservoir, cup- 

 shaped in transverse section. I did not succeed in tracing the blood- 

 sinuses of the typhlosole into connection with any similar blood- 



