2 p. HERBERT CARPENTER. 



suggested.^ I ought, however, to have remembered that in 

 his last-published paper, describing the development of Aste- 

 rina gibbosa, he had definitely (though for the first time) 

 "withdrawn his earlier suggestion ; for I had specially marked 

 the passage in the copy of his memoir which he was good 

 enough to send me. It is as follows : ^ 



" Im Gegensatze zu menier friiheren Aufi'assung, wonach 

 dieses Skelettstiick (i. e. Odontophor) als die erste intermediare 

 Skelettplatte bezeichnet werden miisste, bin ich jetzt zu der 

 Ansicht gelaugt, das dasselbe mit den vorhin besprochenen 

 paarigen Interambulacralplatten in einer Reihe gehore und 

 demnach als unpaare Interambulacralplatte aufzufassen sei." 



Ludwig, therefore, no longer considers the odontophore of 

 an Asterid as homologous with the mouth-shield of an Ophiurid 

 and oral of a Crinoid. I am by no means sure, however, that 

 his earlier view is not the more correct one after all ; but I am 

 quite content to leave this question in the hands of my friend 

 Mr. Sladen, whose opportunities of studying the modifications 

 of the Asterid skeleton have been unrivalled. 



One very important result of his observations is fully ex- 

 plained by himself in the following paper (pp. 29 — 34), and I 

 will do no more than just refer to it. Ludwig's discovery of the 

 true nature of the terminal plates in the Ophiurid arms ^ will 

 be remembered by readers of my fifth note."* The termi- 

 nals (PI. I, figs. 1.2, 13 t) are not " radials " homologous 

 with the ocular plates of an Urchin, as has been generally 

 supposed since the time of Miiller; for, so far as we yet know, 

 the representatives of these plates remain on the disc, some- 

 times close to the dorsocentral, and sometimes separated from 

 it by intervening plates (PL I, figs. 1 — 4, 6 — 9j 4). They 



^ 'Morpli. Stud./ ii, loc. cit., p. 16. " Ueber den prinoaren Steinkanal der 

 Crinoideen, uebst vergleichend-anatomisclien Bemerkuiigen iiber die Ecliiiioder- 

 men iiberhaupt," pp. 42, 43. " Neue Beitrage zur Anatomic der Opbiureu," 

 pp. 66, 79. "Eatwieklungsgescbicbte der Asteriua gibbosa," p. ISi. 



» 'Morph. Stud.,'ii, p. 181. 



' ' Morpb. Stud.,' ii, "Zur Entwicklmigsgeschicbte des Ophiurenskelettes," 

 pp. 97, 98. 



•• Tbis Journal, vol. xxii, new series, October, 18S2, pp. 379, 380. 



