146 E. W. MACBRIDE. 



singling out this as a blood-vessel would appear to be that 

 when he forced an injection into the mass of the ovoid gland 

 he got the colouring matter here. When one thinks of the 

 thin and non-resistent nature of the boundary walls of sinuses, 

 especially in cases of poor preservation, and the little firm 

 tissue (other than lime) there is in the body-wall of Ophiurids, 

 one will not be inclined to place much dependence on results 

 obtained by injection. The radial blood-vessels Kohler finds, 

 consist of fibres, cells, and pigment ; and what strong distin- 

 guishing mark there is between them and the dorsal ganglion- 

 cells of the nerve-cord appears neither from Kohler's figures 

 nor description. 



Cuenot, in his earlier work (4), denies the existence of blood- 

 vessels, and traces cavities lined with cubical epithelium in the 

 gut-wall communicating with the axial sinus. He has also 

 failed to find the Urkeimzellen in the pseudo-heart, and con- 

 cludes that these, when they occur in the rachis, are due to 

 special formation in situ. The spaces he has found are very 

 possibly mucus-cells cut obliquely ; such are greatly developed 

 in the ventral wall of the stomach ofAmpbiura squamata. 

 His failure to trace the primitive germ-cells into the ovoid 

 gland is due to want of study of young specimens. 



In his later work on general Echinoderm morphology (6) 

 he finds one large axial sinus, into which stone canal and pore 

 canal open, confusing thus together, from want of study of 

 good series, ampulla and axial and aboral sinuses. He now 

 accepts Kohler's account of the haemal system. 



As to the development of the ovoid gland in Echinoderms 

 in general, most of the notices 1 have been able to collect are 

 very scanty, and evidently based on one or two observations 

 only. 



Thus in Asterina gibbosa Ludwig (12) finds that it forms 

 as a split in the mesentery containing the stone canal ; in As- 

 ter ias hyadesi Perrier (13) finds that it arises as a conical pro- 

 cess of the peritoneal lining of the stomach, which grows down 

 alongside the wall of the axial sinus, and becomes later inva- 

 ginatcd into its interior. It contains a number of "corps 



