70 CALIFORNIA ACADEMY OF SCIENCES. 



The peritoneal sac consists of very large cells with small, sharply defined and 

 very round nuclei. When these cells are empty they are very transparent and 

 their walls are very plain. There are a few blood vessels on the peritoneal sac, and 

 few of these cover also the folds. 



Nephridia of Kerria (fig. 23). Having recollected Kerria McDonakli in the 

 pond near Miraflores in the Cape Region of Baja California, the only place where it is 

 found to date, I have taken the opportunity to re-examine the nephridia in order to 

 ascertain their resemblance to those of our present form as well as Ocnerodrilus. As 

 a consequence I am able to correct some errors and to add several details. The gen- 

 eral structure is the same as in the Ocnerodrilus and Phcenicodrilus and the windings 

 of the canals the same as in the Argilophilus, etc. The two folds make a large 

 rounded loop upwards, and join posteriorly in a very long spur partly free from 

 peritoneal covering. The bridge connecting the junction of the spur and the 

 posterior fold with the junction of the anterior fold, wide duct and narrow duct, 

 is wide and ciliated, in fact it is the widest part of the canal. Posteriorly the 

 canal of the bridge projects into the spur forming the widest of the four canals in 

 this part. At the apex of the spur two and two of these canals are seen to join as 

 usual, forming two loops, one outside of and above the other. The inner and lower 

 one of these is the bend of the ciliated canal from the bridge, but it does not ap- 

 pear to be ciliated at this point. 



The posterior fold contains as usual three canals, and so does the anterior fold. 

 The rounded stretch where the two folds meet is more irregular in outline, and con- 

 tains more windings than any other part of the fold, tliough not as many as in Ponto- 

 drilus. The nephrostome is connected with the main body by a slender and nar- 

 row tube, the connection being a little in front of the one between the wide duct and 

 the main body. This wide duct is almost straight with only a slight curve away from 

 the nephridium. It becomes slightly wider towards the nephropore, just before 

 reaching which it turns sharply upon itself. 



Another point of considerable interest is the presence of numerous blood 

 capillaries on the nephridia, especially in the peritoneal sac, which they permi- 

 ate. The blood has its origin from two vessels, one from the branch from the ven- 

 tral main vessel and one from the branch from the dorsal main vessels, the two con- 

 necting by capillaries on the nephridial folds. Until now it has been supposed that 

 Ocnerodrilus and Kerria did not posse-ss blood vessels on their nephridia, but this is evi- 

 dently an error as far at least as some species are concerned. Ordinarily these vessels 

 are not visible and not distinct from the peritoneal cell-walls but a staining with 

 orange G. will bring them out at once. 



The generative organs, with one or two exceptions, resemble those in Ocnero- 

 drilus in form and general arrangement, and if it were not for the regular absence of 

 a prostate our species would be considered as a true Ocnerodrilus. The Spermatheca 

 is very large and resembles in general outline that of Ocnerodrilus Beddardi. In 

 species of Ocnerodrilus the spermatheca always stands up and is pressed close to the 



