NEW SPECIES OF OCNERODRILUS. 239 



the extent that it is figured by Beddard in the species 

 described by him. The narrowing or swelling may be to 

 some extent the result of contraction, but it appears at 

 least to be partially a character of the species, as some 

 species do not show it, even in a series of specimens. 



The sacculated intestine commences with somite xii 

 (fig. I, 5. /. ). It is wider in this somite than anywhere 

 else. In the following clitellial somites the swellings are 

 are smaller and in those posterior to somite xix it has 

 reached its normal form, only gradually diminishing to- 

 wards the caudal end (fig. i). The muscles supporting 

 the sacculated intestine and connecting it with the parietes 

 start half way between the septa. Upon the strength and 

 size of these muscles depend the greater or smaller sac- 

 culation of the intestine. 



Vascular System. There are two primary longitudinal 

 vessels, extending from one end of the body to the other. 

 The dorsal pulsating vessel and the ventral non-pulsating 

 vessel (fig. I, d. v. and v. v.). These vessels are con- 

 nected in the usual way in somite ii, and in the posterior 

 somite, forming respectively the pharyngeal and caudal 

 commissure. 



In somites x and xi these two vessels are also con- 

 nected by secondary vessels, forming one pair of hearts 

 in each of the above somites. These hearts are the most 

 prominent features of the vascular S3^stem, whether the 

 worm is alive or cut up in sections. The two pairs are 

 alike. Emanating in the posterior part of the somite, 

 they form large sack-like vessels, especially wide and 

 sack-like close to the dorsal vessel, and tapering down- 

 wards to the junction with the ventral vessel. These 

 hearts are strongly pulsating, expanding and contracting 

 in harmony with the dorsal vessel and the vessels of the 

 pouch. 



