94 CALAMOCRINUS DIOMEDiE. 



conduit a so demander s'il n'v a |>as la un trait d'organisation, essentielle- 

 ment propre a l'otat Uitra-larval de I'Oursin, mais transf^r^ a la forme 

 definitive que recoit celui-ci en se d^veloppant dans son pluteus, ej s'il ne 

 serait pas possible que le diametre aa [the interambulacral space (/) be- 

 tween 1. II, opposite to the ambulacral IV] de"signat la position hete- 

 rologue qu'avait, par rapport a celui-ci, l'Echinoide'e naissant dans son 

 interieur. S'il en est ainsi. le diametre aw serait Son axe primordial, d'ou 

 l'Echinoide'e anrait passe phis tard a line autre qui serait devenn l'axe 

 anterio-postrrieur de 1' animal adulte." 



1 have always contended for this in my discussions on the position 

 of the axis of Echinoderms as determined by the madreporic body. From 

 the time 1 wrote the Embryology of the Starfish,* I Lave claimed that 

 the madreporic body denoted such a natural primordial organic axis, and 

 was placed in the suture of the two ends of the spiral upon which the 

 abactinal system of the young Echinoderm was developed, namely, upon 

 the right water tube. I have only claimed the prominent importance of the 

 axis denoting the suture of the ends of the spiral of the young Echinoderm, 

 and have most distinctly stated that in Spatangoids and other Echinoids, 

 where an apparent anterio-posterior axis is indicated by the presence of 

 the anus in the odd interambulacrum of the bivium opposite the central 

 odd ambulacrum of the trivium, the madreporic body was associated with 

 the right anterior ambulacrum. In so far I agree with the later views of 

 Loven, — for our views are not so radically different as writers on Echino- 

 derms imagine, — as well as the earlier views of Desor and Cotteau. But I 

 have maintained that the regular Echini were still in a so called embryonic 

 stage, in which the anterio-posterior axis was not differentiated, and that, 

 while in the Spatangoids such an axis existed, the presence of the madre- 

 poric body in an interambulacrum did not denote that it was in the right 

 anterior interambulacrum, basing my objections not only on the structure 

 of the Desmosticha, but also on that of the Clypeastroids. For the reasons 

 more in detail 1 would refer to what 1 have said on the subject in various 

 papers on the Embryology ami Classification of the Echinoderms, already 

 cited. 



But as regards the primordial axis "aw" which Loven suggests may 

 be '-essentiellement propre a l'etat intra-larval de I'Oursin," and which, 



* See On the Young Stages of Echini, Bull. Mus. Comp. Zobl., Vol. I p. 279, 1S09 ; Revision of 

 Hi.- Echini, pp. 639, To!. 1871 ; and Report on the Challenger Echinoidea, pp. 4-8, 18S1. 



