146 P. HERBERT CARPENTER. 
so, there is still a certain amount of doubt respecting the 
communication of this organ with the exterior. Even if this 
be admitted, however, the fact still remains that the “canal du 
sable” of Echinus, and the tube to which Koehler gives the 
same name in Spatangus, do not communicate with the same 
vascular ring. The former joins the water-vascular ring 
(auct) which communicates with the tentacular system ; while 
the latter is connected, not with the water-vascular ring of 
Spatangus, but with the blood-vascular ring ; so that even if 
the community of the two vascular systems be admitted, the 
“canal du sable” of the two genera are not homologous, and 
it therefore seems to me very undesirable that they should 
both receive the name which is strictly applicable to one of 
them only. 
Partly in consequence of this want of precision in his 
nomenclature, and partly by the omission of half a dozen 
words in one of my sentences, Koehler has been led to 
comment on what he believes to be an inconsistency between 
two passages which he quotes from my previous paper. In the 
first one,! I expressed the belief that the canal which joins the 
excretory organ in Spatangus with the oral ring, and is 
called by Koehler the “‘ canal du sable,” does not really belong 
to the water-vascular system, but corresponds to the “ glan- 
dular canal” of Echinus. Koehler? remarks that he had 
already pointed out this latter homology, as indeed I had 
stated in my earlier note. But then he goes on to say, “ Puis 
i la page suivante Carpenter ajoute. ‘ Koehler regards the 
stone canal of Spatangus as homologous with the glandular 
canal of Echinus;’” and he endeavours to find in my subse- 
quent remarks an expression of a theory inconsistent with his 
belief and my own. 
What I really wrote was—‘‘ Koehler regards the organ 
which is commonly called the stone canal of Spatangus, 
as homologous with the glandular canal of Echinus, on 
! This Journal, vol. xxiii, p. 607. 
* § Zool. Anzeiger,’ 1885, p. 81. 
> This’ Journal, vol. xxiii, p. 609, 
