2 Dr. P. H. Carpenter on the 



wliich homologies are universally recognized, though the 

 fact does not appear in the nomenclature. 



1. The use of the term "Water-tube." 



The term " water-tube" seems to have been first used by A. 

 Agassiz * for the two coelomic diverticula of the archcnteron 

 in the Starfish-larva, this being " the name which denotes 

 most appropriately the function they assume of circulating 

 water througli the body of the larva." He also applied the 

 same namef to the gills or " papula3 " of Stimpson and 

 Sladen, which are not developed till much later ; but tlie 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 liave 

 been variously known as the coelomic pouches, vaso-peritoneal 

 sacs, &c. ; while " water-tube " or '' tube hydrophore " has 

 been largely used by both English and French writers instead 

 of the misleading terra " sand-canal " or " stone-canal," wliich 

 is so often totally inapplicable to the structure it is supposed 

 to designate. In America, however. Brooks X 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 waiters. 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 anyway give rise to the 

 "water-tubes" of the ambulacral system. Fewkes is an 

 especial oflfender in this respect, for in his last publication but 

 one he uses the term water-tube with diftorcnt meanings on 

 two successive lines § : — " Each of the five small cuh-de-saCj 

 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- 



difF6reuts, crdent, daus I'espnt du lectonr, iiiie confusion p<?uiblo qu'il est 

 parfois difficile d'(5cliiircir par uno seuk' locturo et qui a coutribu^, poiu' 

 uuo largo part, a t'aiie preiulro dans certains cas, coumie diver-routes, des 

 opinions qui ue dilK^raieut pas sensiblenient I'uue de I'autre" (" lieclieivhea 

 sur les llolothuries des Cotes do France," Arch. Zool. Exp. et G«5u. 

 vol. vii. 1881), p. (330). 



* 'EmbrvolopToftlie Starfish,' 1864. Eepriuted in "North Americau 

 Starfislies,""3Iem! Mus. Couip. Zool. 1877, vol. v. p. 13. 



t ll'id p. 62. 



J ' Handbook of Invertebrate Zoology,' Boston, 1882, pp. 72, 13.5. 



§ " On the Developiueut of the Ctdcareous Plates of Ast<'n'as," Bull. 

 Mus. Conip. Zoiil. 1888, vol. xvii. p. 7. 



