256 J. H. ASHWOETH. 



to a less extent, as the blood-vessels which pass between the 

 SLibintestinal vessels and the nephridia and body-wall are 

 capable of considerable extension without injury (see fig. 14j. 



From the level of the fourth diaphragm to that of the four- 

 teenth seta there are six rather long median blood-vessels 

 running from tlie ventral vessel to the tnid-ventral wall of the 

 stomach, and paired segmental vessels pass right and left from 

 the ventral vessel to each parapodiuin (and corresponding 

 nephridium) up to the fourteenth. From the fifteenth seta to 

 the end of the animal there are two segmental vessels, an 

 afferent and an efferent, on each side. 



The nephridia are to a large extent hidden beneath the 

 numerous oblique muscle bands, and even when exposed by 

 dissection are difficult to see, on account of their small size; 

 they ai-e usually only about '25 mm. in diameter. 



10. C(ELOM. 



The coeloni is spacious, especially in the inflated region of 

 the animal. It is subdivided by septa only in the branchial 

 region. In the rest of the body the septa are very small, 

 being represented by a thin strand of tissue running along- 

 side the afferent nephridia! vessel. 



The coelomic fluid is, as far as can be judged from spirit 

 specimens, very similar to that of Arenicola (Gamble and 

 Ashworth, 1898, p. 29, and pi. 5, fig. 24). It contains the 

 reproductive cells in various stages of growth, and coelomic 

 cells, some fusiform about 30 jn long, and others spherical or 

 amoeboid. 



The reproductive cells collect principally in the space 

 between the oblique muscles and the ventral body-Avall, 

 especially in ripe females, in which this space is crowded 

 with ova. 



11. Alimentary Canal. 



Danielssen (1859, p. 69) described the general form of the 

 alimentai-y canal, pointing out its various divisions^ and dvaw- 



