66 CHAETODERMA NANULA. 



spicules being distinguishable. Associated with these are numerous rounded 

 cells (Plate 35, fig. 11) that occur also in the dige.stive gland. In most cases 

 these are free but occasionally one may be seen that is encysted in the cells of 

 the oi'gans mentioned. Rarely they are associated in pairs as though in the 

 process of conjugation. 



The gonad holds the usual position and like the sperms, in all stages of 

 development, presents no noteworthy characters. Posteriorly the halves of 

 the organ diverge, become rather indistinct though their route may be traced 

 with certainty, owing to the presence of spermatozoa, passing lateral to the 

 heart or the expanded base of the aorta and opening into the pericardium. 

 This last named space lacks the almost diagrammatic outline as in C. nitidu- 

 lum and is much more limited in extent, but its relations to the gonoducts are 

 very similar. 



Chaetoderma nanula, sp. nov. 



One specimen of this species was dredged off the coast of southern California 

 (Sta. 4369) at a depth of 260-284 faths. It is 9 mm. in length by 0.9 and 1.2 

 the average diameter of the metathorax and preabdomen respectively (Plate 4, 

 fig. 1). The color of the globular, protrusible portion of the prothorax is light 

 brownish yellow (though this may have been produced by tannin from the cork) , 

 while the metathorax and preabdomen are considerably darker, the latter region 

 becoming olive-green. A dark brownish substance incrusts the spines about the 

 cloacal opening. The hypodermal layer is comparatively thin, the cells small 

 and somewhat indistinct, yet are typical so far as may be determined. The 

 spines are represented (Plate 37, fig. 18). 



The mouth opening represented (Plate 4, fig. 12), leads into a relatively 

 spacious tube lined with slender columnar cells except along the dorsal side where 

 they are almost cubical. A median fold, located immediately in front of the 

 radula, probably represents a subradular organ since it is typically innervated. 

 Salivary glands are almost wholly lacking, a small group attached to the pharyn- 

 geal wall adjacent to the radula being all that is visible in the present specimen. 

 The radula is small but typical. Beyond it the tube narrows considerably, 

 the lining becomes folded and in this form it unites with the stomach. At the 

 outset this last named organ is plain walled but near its union with the liver 

 becomes considerably sacculated. The intestine is distended with fragments 

 of Radiolaria, sponge spicules, and organic debris. Parasitic Protozoa, resem- 

 bling those from Chaetoderma calif urnica, are abundant and are imbedded in the 

 epithelial lining of the stomach, intestine, and liver throughout their entire extent. 



