600 P. HERBERT CARPENTER. 



Teuscher/ who failed, however, to distinguish the radial blood- 

 vessels in the ambulacra, confounding them with the so-called 

 perineural spaces. The two vessels are readily visible on the 

 inner aspect of the ambulacra, each sending branches to the 

 ampuUse, and may be injected with different materials ; while 

 their distinctness, though not apparent in Teuscher's section 

 of the ambulacra, is quite evident in that figured by Koehler. 



According to Teuscher, the water-vessels of the ambulacra 

 ascend the outside of the lantern to join the ring at its summit, 

 just as Perrier described them; while the blood-vessels pass 

 over the actinal membrane towards the mouth, ascend along 

 the pharynx, between it and the interpyramidal muscles, and 

 join the superior of the two rings, in which the intestinal vessel 

 originates. Koehler, however, also working by the section 

 method, has been unable to find these radial vessels described 

 by Teuscher on the pharynx, and his injections have not led 

 him to suspect their presence. ^ In fact, he says distinctly that 

 at the edge of the peristome '' les vaisseaux ambulacraires, de 

 doubles qu'ils etaient, deviennent simples et forment alors les 

 cinq branches qui montent sur la face-externe de la lanterne, 

 et vont aboutir au cercle perioesophagien inferieur" {i.e. water- 

 vascular ring). 



It is noteworthy, however, that in the Spatangids either of 

 the two oral rings, internal or external, may be injected from 

 the corresponding radial vessel, and Koehler says distinctly 

 that each of these rings sends branches into the ambulacra.^ 

 This leads to the suspicion that each radial vessel of an 

 Echinus communicates directly with a corresponding vascular 

 ring, just as was described by Teuscher, and that the water- 

 vascular and blood-vascular systems are distinct, at any rate in 

 the peristome and ambulacra. 



Koehler's memoir would have been still more valuable than 

 it is, had he entered more fully into a comparison of his results 



1 " Beitriigc zur Anatomic dcr Echinodermcn," iv, ' Echinidae. Jen. Zeitschr./ 

 Bd. X, pp. 520—521, Taf. xx, fij?. 0. 



2 Op. cit., pp. 70, 73. 



3 Op. cit., p.p. 93, 94, 100. 



