558 FRANK E. BEDDARD. 



The longitudinal muscular coat consists, like that of other 

 earthworms, of fibres embedded in a matrix of connective 

 tissue. As I have already mentioned (supra, p. 545), this con- 

 nective tissue forms a thickish layer below the level where the 

 muscular fibres end ; it is in this layer that the longitudinal 

 vessels run. At the implantation of the couples of setse the 

 longitudinal vessels come to lie within the arch formed by the 

 two setffi — which converge at their deep ends, and diverge super- 

 ficially. Just behind the setse the longitudinal vessel gives oflFa 

 wide branch, which gradually gets nearer and nearer to the thin 

 peritoneal epithelium. Ultimately (fig. 7) it comes to lie within 

 the body-cavity, surrounded at first by a prolongation of the 

 almost hyaline connective tissue of the longitudinal muscular 

 layer. This covering finally disappears, and the tube comes to 

 an end ; in a few cases I have traced it into connection with a 

 very rudimentary coil of uephridial tubules. I have already 

 mentioned that in the clitellar segments the nephridia are not 

 visible with a lens. The tube lying within the coelom was 

 always accompanied by a blood-vessel of about the same dia- 

 meter, and I have observed the two to be suspended by a 

 common mesentery. The longitudinal vessels are also pro- 

 vided with numerous branches, which pass among the longi- 

 tudinal muscles ; some of these branches are smaller, some 

 larger ; a few of the larger ones pass obliquely upwards in the 

 direction of the circular muscular layer ; the tract which these 

 branches traverse is free from muscular fibres; traced up- 

 wards, these branches are seen to open into a circular 

 vessel, which runs right round the body; these circular 

 vessels, which are repeated metamerically, lie just between the 

 circular and longitudinal muscular coats, close to an important 

 nerve, which also passes right round the body (see fig. 20). 

 The circular vessels are of considerable width, and can be easily 

 recognised in sections examined by quite low powers; their 

 outline is somewhat crenated, which probably means that they 

 can be expanded or retracted in accordance with the move- 

 ments of the body. The fact that the vessel lies between the 

 two muscular coats, instead of within the substance of one of 



