242 CALIFORNIA ACADEMY OF SCIENCES. 



which species the dorsal secondary vessel in somite ix 

 is transformed to a connecting vessel between the ventral 

 and dorsal vessel, similar to a heart (figs. 31 and 38, c. vl.) 

 but of less thickness and more cyHndrical throughout its 

 length. A gastric secondary vessel supplies the saccu- 

 lated intestine. It leaves the dorsal vessel anteriorly to 

 the other branches almost in the center of the somite, or 

 half-way between the septa. It develops into a large 

 gastric system, especially prominent in the somites of the 

 clitellum. 



There are no blood-vessels on the nephridia. 



The septal glands are furnished liberally with blood- 

 vessels, emanating in each somite from the lateral vas- 

 cular trunks (fig. i, v.). As will be seen, the vascular 

 system in Ocnerodrilus resembles greatly that of Gordio- 

 drilus, especially in having the dorsal and ventral vessels 

 only connected in somites x and xi (or in ix, x and xi). 



Ncfhridia. The nephridia are present in all the 

 somites, commencing with somite iv. The anterior four 

 nephridia are very small, degenerate, devoid of or with 

 very few peritoneal cells. The nephridium in somite iv 

 is the smallest, the one in the vi is larger and the one in 

 somite viii the largest of all the anterior nephridia. The 

 nephridium in somite ix is always very large and fur- 

 nished with copious masses of peritoneal cells. This may 

 possibly be in some way dependent upon the supposed 

 connection between this nephridium and the diverticulum 

 in this somite. 



The nephridia in somites x and xi are smaller, some- 

 what degenerate, but not to the extent as described by 

 Beddard in O. Eiscni, but still covered with peritoneal 

 cells which stain differentl}^ from the surrounding sperm- 

 sacs. The nephridia posterior to somite xii are all cov- 

 ered with peritoneal cells. They rather increase in size 



