606 p. HEiiBEET CARPEWTER. 



In the Sptitangids, as in the Urchins, Hoffmanii^ was only 

 able to find one vascular ring around the mouth, that of the 

 ambulacral system. He described the ventral vessel as not 

 originating in this ring, but as communicating with it by a 

 special connecting branch ; while he was unable to differen- 

 tiate the water-tube from the so-called " heart,^' of which, 

 however, he recognised the glandular nature. 



Teuscher 2 satisfied himself of the existence of another vessel 

 than the water-tube at the side of the gullet, but failed to make 

 out its connections in the peristome. It corresponds to the 

 " glandular canal " of Echinus. Working downwards from 

 the madreporite, he found the " heart " or gland with the water- 

 tube close to it. The latter is readily recognisable by its lining 

 of columnar epithelium, and lies closer to the gland than in 

 Echinus. At the lowest part of the gland, where the water- 

 tube dilates slightly, Teuscher finds *' seine innere dem Herzen 

 anliegende Wand immer stark verdiinnt. . . . Der Stein- 

 canal nachdem er am Herzen voriibergegangen ist, wird von 

 einem oder zwei feinen Gefassen begleitet.'^ It then passes 

 downwards underneath the diverticulum to reach the gullet. 

 There is some obscurity in this description, as there also is in 

 that given by Koehler, but the two partially interpret one 

 another. In Spatangus, as in Echinus, Koehler found two 

 vascular rings round the mouth, each with radial extensions 

 into the ambulacra. But he describes the communicating 

 branch from the internal marginal vessel as connected with 

 both rings. ** Simple sur presque toute sa longueur, elle se 

 bifurque a son extremite et chacune des deux branches se jette 

 dans un des cercles peribuccaux." This is improbable, to say 

 the least of it, for in no other Echinoderm are the visceral 

 vessels known to communicate with the water-vascular ring. 

 Doubtless, however, it does not surprise Koehler, who does 

 not distinguish between blood-vascular and water-vascular 

 systems. But as this point is important, one regrets that he 



1 " Zur Aiiiilouiio dcr Ecliiiicu uiid S|)ataugtii," ' Nicdcrl. Arcb. dc Zool.,' 

 Bd. i, pp. 10—112, Taf. iii— x. 

 * Loc cit., pp. 631 — 534. 



