2 
Dr. P. II. Carpenter on the 
which homologies are universally recognized, though the 
fact does not appear in the nomenclature. 
1 . The use of the term “Water -tube" 
The term u water-tube” seems to have been first used by A. 
Agassiz * * * * § for the two coelomic diverticula of the arclienteron 
in the Starfish -larva, this being u the name which denotes 
most appropriately the function they assume of circulating 
water through the body of the larva.” He also applied the 
same name t to the gills or “ papulae ” of Stimpson and 
Sladen, which are not developed till much later ; but the first 
meaning which he gave to the term has not found acceptance 
in Europe, especially since the morphological importance of 
these water-tubes has been more fully realized, and they have 
been variously known as the coelomic pouches, vaso-peritoneal 
sacs, &c. ; while u water-tube ” or u tube hydrophore ” has 
been largely used by both English and French writers instead 
of the misleading term u sand-canal ” or u stone-canal,” which 
is so often totally inapplicable to the structure it is supposed 
to designate. In America, however, Brooks J and Fewkes 
have continued to speak of the water-tubes of the Echinoderm- 
larva, and they use the same term when referring to the organs 
which are described as circular and radial water-vessels by 
European writers. This course seems likely to lead to much 
confusion, the more so as one at least, and sometimes both, of 
the larval coelomic pouches do not in any way give rise to the 
(e water-tubes ” of the ambulacral system. Fewkes is an 
especial offender in this respect, for in his last publication but 
one he uses the term water-tube with different meanings on 
two successive lines § : — u Each of the five small culs-de-sac , 
r w } from the water tube on the ambulacral side of the young 
starfish forms a radial water tube of the starfish.” Five 
pages later he says that the stone-canal is an internal calcifi- 
differents, orient, dans l’esprit du lecteur, une confusion pdnible qu’il est 
parfois difficile d’dclaircir par une seule lecture et qui a contribue, pour 
une large part, a faire prendre dans certains cas, comme divergentes, des 
opinions qui ne difteraient pas sensiblement l’une de l’autre” (“Recherehes 
sur les Holotburies des Cotes de France/’ Arch. Zool. Exp. et Gen. 
vol. vii. 1889, p. 630). 
* ‘ Embryology of the Starfish/ 1864. Reprinted in “ North American 
Starfishes/’ Mem. Mus. Comp. Zool. 1877, vol. v. p. 13. 
t Ibid. p. 52. 
j ‘ Handbook of Invertebrate Zoology/ Boston, 1882, pp. 72, 135. 
§ “ On the Development of the Calcareous Plates of Asterias /’ Bull. 
Mus. Comp. Zool. 1888, vol. xvii. p. 7. 
