134 PROCEEDIN'GS OF THE ACADEAIY OF [Feb., 



endothelium is to recognize. The distinction between Dinophilus and 

 the Turbellaria is much greater, if it is compared to the larvae of the 

 latter. Yet the resemblance should be greater if, as Korschelt sup- 

 poses, Dinophilus be a primitive Turbellarian form. ' ' 



The weight of the evidence furnished by our present knowledge of 

 the morphology and embryology of the annelids, as well as that of 

 Dinophilus, is, I think, heavily in favor of a close relationship of the 

 latter with the annelids. There is scarcely a character in the structure 

 of Dinophilus which is not held in corhmon with some member of that 

 group. The general external form, including the distribution of the 

 cilia and the caudal appendage, are found in several annelid larvae, 

 such as Harpochceta (Korschelt, 1893); the ciliated rings may persist to 

 maturity, as in Ophyrotrocha (Korschelt, 1893) and Nerilla (Perey- 

 aslawzewa, 1896), as well as in Protodrilus (Hatschek, 1880). The 

 metamerism is also like that of the annelids, expressed by the same 

 organs — with the exception of those arising from the mesoderm bands — 

 and developed in the same manner, as the investigations of Schim- 

 kewitsch (1895) and myself (1904a) have shown. The nephridia are 

 precisely like those seen in many annelid larvae. Moreover, Shearer 

 (1906) has recently found that the nephridia of D. tceniatus possess the 

 ■curious structures termed by Goodrich (1898) "solenocytes," and 

 found by him characteristic of many members of the Polychceta. The 

 type of the nervous system of Dinophilus is unquestionably the em- 

 bryonic annelid type; even its distinctive features, such as its epithelial 

 position and the wide separation of the two halves of the ventral cord , 

 are found not only in larval stages, but also in adult stages of several 

 members of the Annelida. The preoral commissure of D. conkMni 

 can also, I think, only be satisfactorily explained by deriving it from 

 the nerve ring of the trochophore larva. The alimentary canal is, in 

 its main features, strictly comparable to that of the annelids; while the 

 proboscis, in its general structure, is like that of many Polychceta, as, 

 for example, the Eunicidie (Lang, 1891). 



A possible relationship with the Rotatoria has been pointed out by 

 several investigators; of these probably Schimkewitsch (1895) has 

 stated the case for the rotifers most clearly. After a very fair pre- 

 sentation of the claims of Dinophilus to a place among the annelids, 

 he says : 



"Ohne Zweifel sind auch einige Ziige vorhanden, die Dinophilus 

 mit den Rotatorien verbinden: die furchung des Eies, die Anwesen- 

 heit des Schwanzanhanges, der mit dem Fusse der Rotatorien iiberein- 

 stimmt, der geschlechtliche Dimorphismus ; man muss auch gestehen, 



