NOTES ON THE ECHINODBRM MORPHOLOGY. 599 



extended to the Spatangidse, which appear to present certain 

 anomalous characters, as yet hut imperfectly understood. 



It will be remembered that Perrier, like Hoffmann, could 

 only find one vascular ring round .the mouth of an Echinus; 

 and he described it as connected, not only with the water-tube 

 and radial water-vessels, but also with the ventral vessel of 

 the gut. The results of his injections of the so-called heart 

 led him to assert that it is " tres nettement termine vers le bas 

 et qu'il n^en sort aucun canal. II ne peut done etre question 

 d'un vaisseau inferieur parallele au canal du sable et aboutis- 

 sant d l^un des deux cercles vasculaires que Ton suppose existev 

 autour de I'cesophage."^ 



Koehler finds, however, that by inserting his cannula into the 

 lower end of this organ, which, like Perrier, he calls the 

 " ovoid gland," he is able to inject a vessel lying alongside the 

 water-tube, but totally distinct from it. He calls it the 

 " glandular canal," and finds it to be connected with an oral 

 ring in which radial vessels originate. These are not the 

 water-vascular ring and radial water-vessels, which can be 

 injected from the water-tube altogether independently of those 

 described by Koehler. He says that the glandular canal can 

 be readily followed with the aid of a lens, right up from the 

 lantern to the apex of the ovoid gland. He speaks of it as 

 containing blood, and has frequently found coagulum both in 

 it and in its ramifications over the peripheral part of the ovoid 

 gland. When this glandular canal is carefully injected, the 

 fluid enters the circumoral ring before mentioned, together with 

 the internal marginal vessel which is connected with it, and 

 not with the water-vascular ring as formerly described. The 

 injection also passes into arborescent ramifications Avithin the 

 Polian vesicles ; but if pressure is used, it fills these organs 

 and enters the water-tube and radial vessels.^ 



This second oral ring seems to have been previously seen by 



1 " Reclierches sur I'apparcil circulatoire des Oursins," 'Arch. do. Zool. 

 exp. et. gen.,' t. iv, 1875, p. 013. 



2 Op. cit., pp. 65-70. 



