NOTES ON THE ANATOMY OF STEliNASPlS. 233 



Notes on the Anatomy of Sternaspis. 



By 



Edwin S. Ooodi'icli, IS.A., 



Assistant to tlie Linacre Professor, Oxlord. 



With Plates 15 and 16. 



In the beautiful works both of Professor Vejdovsky (5) and 

 of M. Rietsch (3) on Sternaspis we find certain statements 

 which, if correct, would place that worm in a very exceptional 

 position. These authors describe the excretory organ as a 

 lobulated sac with neither internal nor external opening, and 

 the genital organ as a somewhat similar sac entirely shut off 

 from tiie coelom, but opening to the exterior by two long ducts 

 witli which the sac is directly continuous. Thus Sternaspis, 

 in having a completely closed excretory organ (nephridium?), 

 and in having the ovary or testis situated in a special cavity 

 without communication with the coelom, would differ from all 

 known Polychaeta, of which group it is no doubt a highly 

 modified member. 



It was, therefore, with a view to either confirm or correct 

 these descriptions that I began a study of Sternaspis thalas- 

 semoides. Otto, during a recent visit to Naples. I may say 

 at once that they both proved to be erroneous. 



To these observations have been added some notes on the 

 cuticle and muscular system. 



The Genital Organs. — Fig. 1 represents, somewhat dia- 

 grammatically, a ventral view of the ovary, or ovisac, as it 



