On the Paired Dorsal Vessel of Certain Earthworms. 429 



In the third species, which is very different in its anato- 

 mical as well as external characters from either of the two 

 described above, the dorsal vessel was still more completely 

 separated into two distinct tubes ; these only united together 

 to form a single trunk upon the gizzard, which in this as in 

 so many other earthworms is situated close behind the 

 pharynx, and not at the junction of the oesophagus with the 

 crop as is the case with Liunhriciis. The two dorsal vessels 

 appeared to pass to the posterior extreme of the body with- 

 out being connected by any anastomoses or transverse vessels ; 

 in traversing the mesenteries they also retained their dis- 

 tinctness, and were not fused together at these points as in 

 the last-mentioned species. In this earthworm, therefore, 

 the dorsal vessel retains its (presumably) embryonic character 

 much more completely than in any of the other three species 

 to which I have referred above. I should add that, in every 

 case, the results recorded do not dejoend upon the dissection 

 of a single individual, but upon two or more ; they are not, 

 therefore, likely to be abnormal. 



The above described facts are illustrated in the two drawings 

 which I exhibit (PL XXIL, Figs. 2, 3). Fig. 2 is a sketch of 

 the circulatory system in the anterior part of the body, from 

 which the lateral trunks as well as the peripheral circulation 

 generally has been omitted in order to avoid undue compli- 

 cation. I may, however, take the opportunity of calling 

 attention to some other facts in the circulatory system of 

 Aeanthodrihcs, of which there are no published descriptions. 

 The dorsal vessel is connected directly with the ventral 

 vessel by eight pairs of transverse trunks, of which the five 

 anterior spring from the dorsal vessel itself; the three 

 posterior pairs, which are considerably larger and stouter than 

 the anterior, spring not from the dorsal vessel itself but from 

 a small trunk which lies beneath it and immediately upon 

 the intestine; this vessel has been termed by Perrier the 

 supra-intestinal, and its connection with the posterior "hearts" 

 has been recorded to exist in many other genera of earth- 

 worms ; ^ in the second species of Aeanthodrihcs to which I 

 have referred in the present paper, the arrangement of the 



^ Arch, de Zool. Exp., t. iii., t. ix. 



