1907.] NATURAL SCIENCES OF PHILADELPHIA. 125 



lar portion, the coll wall covering this process serving as the walls of the 

 iluct. This duct, as indicated above, is filled with a brownish excre- 

 tion. 



Embeddetl within the cytoplasm which surround the diagonal and 

 transverse canals are found greenish refringent bodies (figs. 25c, 25d, 

 and 26ft, r.h.) of an irregular ovoid shape, and similar in general ap- 

 pearance to those seen in the nephridia of the posterior segments. In 

 the nephridium represented in text fig. IV and figs. 25c and 2od there 

 are two of these, of nearly the same size. In the nephridium repre- 

 sented in figs. 26a and 266 there are also two subequal refringent bodies, 

 and in addition a denseh^ staining inclusion. 



From the foregoing description it is seen that in the first pair of 

 nephridia of Dinophilus conklini we have to do with relatively complex 

 and highly differentiated structures. A contemplation of text fig. 

 R' will show, however, that these nephridia are derived from simple 

 nephridia, of the type termed by Hatschek (1888) "protonephridia," 

 like those of the four succeeding pairs, by a growth and differentiation 

 of their component cells, chiefly at two points, namely, those occupied 

 by the glandular bodies. The blind ciliated anterior end is clearly to 

 be recognized as the inner or central end of the simple nephridium, 

 and the canalar plexuses, with their connecting transverse and oblique 

 canals, as its middle part. Obviously one of these connecting canals is 

 of secondary origin and one of primary, corresponding to the original 

 lumen of the primitive nephridium. The size of the diagonal canal, 

 and the fact that its connection with the lateral glandular portion is 

 some distance removed from the union of the latter with the inner 

 canal, speaks in favor of its being the representative of the primitive 

 hmien; the transverse canal would then have to be considered as a 

 sort of short cut for the products of excretion from both the inner 

 canal and the lateral glandular portion of the nephridium. The 

 terminal duct has also evidently undergone modification in that its 

 external opening has been shifted forward to the edge of the mouth. 



The function of the glandular bodies with, the contained canalar 

 plexuses can only be guessed at. It is at least certain that it is one 

 not performed by the other nephridia. That this function is truly of a 

 glandular nature is indicated by the fact that the ducts are always 

 filled by a homogeneous substance of a brownish color, much resembling 

 mucus in appearance. 



The highly differentiated groups of the OUgochceta and Hirudinea 

 alone appear to exhibit conditions comparable to those seen in the 

 anterior pair of nephridia of Dinophilus conklini. A breaking up of the 



