126 Transactions. — Zoology. 



Internal Anatomy. 



As in other earthworms, the cavity of the body is sub- 

 divided by a series of transversely disposed muscular septa, 

 inserted into the body-wall at the level of the intersegmental 

 furrows, and attached to the wall of the gut at their inner 

 edges. Of these septa, those forming the posterior boundary 

 of the segments 8 to 12 are much thicker than the others. 

 The dorsal blood-trunk is duplicated, but the two tubes unite 

 as they pass through the septa. In addition to this main 

 blood-trunk there is, below it and closely connected with the 

 wall of the gut, a " supra-enteric " vessel in a few of the 

 anterior segments — about 9 to 14 — and it is this supra-enteric 

 vessel that gives off the four pairs of intestinal hearts, or, 

 better, " enteric hearts," which have no connection with the 

 "dorsal" vessel. These "hearts" occur in segments 10-13; 

 each passes round the gut to enter the ventral vessel be- 

 low the gut. In segments 8 and 9 are two pairs of " lateral 

 hearts," arising from the dorsal vessel and passing to the ven- 

 tral ; these are, however, smaller and less conspicuous than 

 the other hearts. In the 9th segment the dorsal trunk gives 

 origin to a pair of "lateral" vessels, which run forward on 

 each side of the gut, to break up into a plexus on the 

 pharynx. 



The alimentary canal consists of the usual parts. The 

 following dispositons, however, are to be noted : The gizzard 

 occupies the 6th segment ; the oesophagus is a cylindrical tube, 

 extending back to the 17th segment, where it passes into the 

 intestine. In the course of the oesophagus there are marked 

 dilatations in the 14th, 15th, and 16th segments. The walls 

 are highly vascular, and thrown into folds (lamellae) internally; 

 the " oesophageal glands," however, contain no lime, as do the 

 calciferous glands of many earthworms. The size of these 

 " glands " is somewhat variable. The intestine is much wider 

 than the oesophagus, is thin walled, and possesses a very slight 

 ridge-like typhlosole. 



The nephridia are fairly typical, and call for no. special 

 remark here ; be it noted, however, that there are evident 

 differences between the dorsal and ventral series of nephridia. 



The reproductive system is, however, of importance, as it 

 is characteristic of the family Acanthodrilida. "We have, of 

 course, to distinguish the male organs and the female organs. 



(a.) The Male Organs : There are two pairs of testes, lying 

 in segments 10 and 11 respectively, and attached to the an- 

 terior wall of each of these segments. They are quite free, 

 not enclosed in sacs, as is Lumbricus. In the same segments 

 lie the two pairs of funnels of the sperm-ducts, projecting from 

 the posterior wall, or septum, of each of these segments. Two 



