ON MEGASGOLEX CCEEULEUS. 67 



vessel of its own side (figs. 4 — 6). These four pairs of hearts 

 are much larger than any of the other hearts ; they are moni- 

 latedj and the muscular bulbs at their distal extremities are 

 placed at the junction with the ventral vessel in each case ; 

 there are consequently no branches, for, as I have stated above, 

 no branch ever arises from a heart proper. (Note in this con- 

 nection the different behaviour of the intestino-tegumentary 

 vessels in segments x to xiii ; see fig. 4.) 



Capillary Networks.^ — It will be most convenient to 

 consider these before speaking further of the vessels which 

 put them in connection with the above-mentioned trunks. 



We can, I think, recognise two groups of capillary networks 

 only — peripheral networks and intestinal networks. I mean 

 that there are no such things as special commissural networks 

 placing any of the great trunks in communication with one 

 another. If such special networks as have been described by 

 various authors exist, placing the big longitudinal trunks in 

 communication with one another, they may be suitably termed 

 commissural networks. The most important of these which 

 has been described is the network into which the dorsal vessel 

 breaks up at the anterior extremity of the body, and which 

 comes into relation with a similar network arising from the 

 ventral vessel. But in Megascolex, at any rate, I see no reason 

 why this should not be grouped with the peripheral networks. 

 I wish, indeed, to bring into prominence the fact that we have, 

 iu the most anterior region of the body, only a series of seg- 

 mentally arranged networks — nothing, in short, which differs 

 from what obtains in other segments of the body. It must, 

 however, be borne in mind that my investigations have been 

 made upon a worm devoid of subneural and latero-neural 

 vessels, the presence of which may entail other variations. 



The networks which connect the dorsal vessel with the sub- 



' Perrier (9, p. 466, foot-uote) very justly points out that the term "capil- 

 lary " is here used iu a special sense, as there is nothing like the difference 

 between a so-called capillary and a small vessel that obtains iu a vertebrate 

 animal ; but the same remark applies with equal force to the use of the term 

 iu all animals other than vertebrates. 



