OCR Text |
Show 820 MR. F. E. BEDDARD 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 distinguished 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 calciferous glands ; in front of the calciferous glands the oesophagus does not appear to be ciliated. The intestine is unprovided with cseca or with glands of any description. The typhlosole has a characteristic form, and serves to distinguish A. multiporus on the one hand from A. nova zelandia, and A. dissimilis 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 jo of the lumen of the intestine ; in certain regions the typhlosole was a little more complicated, being bifurcate at its extremity, indicating an approach to the structure of the typhlosole of A. multiporus. 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 11 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 may 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. The 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 L U I . 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 particular the lining epithelium of the intestine. Between the cells which form the opposite walls of each of the three folds is a continuous blood-sinus, which widens out at the csecal 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- |