148 P, HERBERT CARPENTER. 
communicates with the exterior, I certainly never spoke of it 
as the stone-canal, as quoted by Koehler. On the other hand, 
I believe that Teuscher was right in giving this name to the 
canal with columnar epithelium at the apical pole. Koehler 
agrees with both Teuscher and myself in considering it as 
homologous with the dorsal end of the “ canal du sable” in an 
Echinus. But he nevertheless prefers to give this name to 
the homologue in Spatangus of a totally different structure, 
viz. the glandular canal of Echinus. ‘This appears to me to 
be very undesirable. The expressions stone (or sand) canal, 
water-tube, Steincanal, canal du sable, &c., have hitherto been 
understood as referring to the tube which joins the primary 
“dorsal pore” of an Echinoderm larva with the developing 
water-vascular ring and its tentacular apparatus. This 
remains as a continuous tube in Echinus, alongside the 
ovoid gland and its connections at bothends. In Spatangus, 
however, only the extremities of this primary tube are left, the 
middle portion having disappeared. Koehler admits this ;! but 
nevertheless he transfers the name “canal du sable” to 
another structure altogether, which, on his own showing, is in 
no communication whatever with the water-vascular ring and 
tentacular apparatus; and for the undoubted homologue of 
which in Echinus he would not think of using the name 
canal du sable. 
We have already seen that Perrier’s statements respecting 
the relation of the ovoid gland of Echinus with the exterior 
have been repeated by Koehler, who now speaks of them as 
“relations qu’on ne peut nier puisqu’on voit dans les injec- 
tions, la matiére se répandre au dehors a travers les pores de 
la plaque madréporique.’’® I hope that I shall not be con- 
sidered discourteous if I still avow myself a sceptic upon this 
point; and I will try to explain my reasons for my doubts. 
They are of two kinds, partly theoretical and partly practical. 
In the present state of morphological teaching it is the 
general practice to put before the student a series of typical 
1 *Zool. Anzeiger,’ 1885, p. 82. 
? * Zool. Anzeiger,’ 1885, p. 81. 
