NOTES ON THE ANATOMY OF STERNASPIS. 239 



sacs of tlie Eiulrilidae described by Beddard (1) are an in- 

 stance of the same thing occurring in connection with the 

 female organs. Throughout the higher Vertebrata the male 

 genital cells are shed directly into the ducts ; whilst in certain 

 cases — as, for instance, many Teleostean fish and the mouse — 

 the ovary is likewise shut off from the body-cavity, being 

 enclosed in a sac in direct continuity with the duct to the 

 exterior. It is, indeed, amongst the Mammalia that we find 

 perhaps the closest parallel with the state of things described 

 above in Steruaspis. In the female racoon (Procyon) or 

 badger (Meles) the ovary is overgrown by a fold of the peri- 

 toneum (" broad ligament") and the funnel of the Fallopian 

 tube, leaving only a narrow aperture communicating with the 

 general coelom (cf. A. Robinson, 4). The steps intermediate 

 between the ordinary condition in Polychsetes, in which the 

 gonad is situated close to the wide-mouthed peritoneal funnel, 

 and the condition in Sternaspis, in which the gonad is enclosed 

 by the funnel, are easy to conceive. 



The Cuticle, Ventral Shield, and Chsetse. — The 

 cuticle of Sternaspis has been well described by Vejdovsky 

 and Rietsch. It is very thick, and consists mainly of inter- 

 crossing fibres. On the outer surface, however, is a thin layer 

 of somewhat different nature, to which are fixed numerous 

 sandy (chiefly siliceous) particles (fig. 24). In this respect 

 Sternaspis resembles the Chlorhoemids, in which the cuticle is 

 also covered with sand. These foreign particles are chiefly 

 grouped round the base of the numberless little papillae Avhich 

 cover the surface of Sternaspis, and are especially numerous 

 and coarse behind the seventh segment. On the anterior re- 

 tractile segments the particles are finer and fewer in number. 



Both inner and outer layers of the cuticle are insoluble in 

 alcohol and ether. The thin outer layer is insoluble in 

 hydrochloric acid, but soluble in strong solution of caustic 

 potash. On the other hand, the thick inner layer is soluble 

 not only in potash and hydrochloric acid, but also in boiling 

 distilled water. It therefore resembles the cuticle of the 

 earthworm (2). 



VOL. 40, PART 2. NEW SER. S 



