120 Transactions. — Zoology. 



found in many species of Lumbricus and Allolobophora, but is 

 comparatively rare elsewhere. "With regard to the vascular 

 system, the only facts which I am able to record are — (1) the 

 condition of the dorsal vessel ; (2) the number and connection 

 of the ' hearts.' The dorsal vessel is a completely-double 

 tube, with the >exception of that portion which lies in the first 

 four or five segments. It resembles the dorsal vessel of 

 Acanthodrilus multiporiis in the fact that the tubes are per- 

 fectly separate throughout, except where they become per- 

 manently fused at the anterior extremity of the body. The 

 somewhat contracted condition of the worm frequently caused 

 the two halves of the dorsal vessel to become widely separate 

 in the middle of each segment, while at the mesenteries they 

 come into close relation : there is, however, no fusion of the 

 two tubes at these points, such as occurs in A. nova-zealandia 

 and Hicrochceta. I observed six pairs of lateral ' hearts,' 

 the last pair being in segment xiii. ; the last four pairs are 

 specially large, and are connected with the supra-intestinal 

 as well as with the dorsal vessels. The anterior two pairs 

 (there are probably one or two pairs in addition to those I 

 have mentioned) are much more slender, and only connected 

 above with the dorsal vessel. 



" Septa. — The septa separating segments viii.-ix., ix.-x., 

 x.-xi., xi.-xii., xii.-xiii., are thicker than the rest, but not to 

 so marked a degree as is often met with in earthworms. 



" Alimentary Tube. — The pharynx has the usual characters. 

 The gizzard lies in segments vi. and vii. ; the oesophagus is 

 thick-walled and highly vascular, but there appeared to be no 

 distinct calciferous glands. The intestine has a typhlosole. 

 The nephridia are not obvious on dissection except in segments 

 ii., hi., and iv. ; in each of these segments is a tuft of hephri- 

 dial tubules of considerable size; in the posterior segments 

 nephridia are present, and open on to the exterior by several 

 pores in each segment. The nephridial system of this worm 

 is in fact like that of Acanthodrilus multiporm. 



" In Dcinodrilus the dorsal blood-vessel is surrounded by a 

 special ccelomic space in a way that is, at present, unique 

 among earthworms. This space does not appear to exist in 

 the first fifteen segments ; after this point the two dorsal 

 blood-vessels are not as plainly visible on a dissection of the 

 worm as they are anteriorly ; the red colour of the blood is 

 masked by the whitish colour of the tissues which form the 

 walls of the perihaemal space. The fact that the blood-vessels 

 are so clearly seen on dissection in the anterior segment 

 leads me to infer that here there is no perihaemal ccelomic 

 space ; but I am unable to support this view by the micro- 

 scopical appearance of the dorsal vessels in this region of the 

 body, which I have not investigated by sections. The enclosure 



