Morphology o/" An ted on rosacea. 29 



Ecliinodcrms, and are very darkly coloured. They are similar 

 in all essential respects to the muscular fibres of the Ophiurids, 

 as figured by Simroth * ; while the fibres uniting the first 

 radials with the centro-dorsal and with one another are of the 

 same nature as those which Simroth described as effecting 

 the various forms of synostosis between different plates in the 

 skeleton of an Ophiurid (p. 435) . 



Messrs. Vogt and Yung do not give any reason for the 

 presence of muscles between plates which are " fusionnes " 

 with one another, and are therefore immovable, neither do 

 they describe any articular faces on which movement can take 

 place. As a matter of fact the fusion or synostosis is often 

 so close that the calyx will resist prolonged boiling in strong 

 alkali and begin to undergo chemical disintegration without 

 the radials separating from one another and from the centro- 

 dorsal ; while any attempt to separate them by a fine knife- 

 blade results in fracture of the whole calyx. Since the 

 ordinary muscles outside the calyx are the very first tissues 

 to be affected by the action of the alkali, the muscles described 

 by Vogt and Yung within the calyx must differ from them 

 altogether in their chemical as well as in their histological 

 features. 



It has been mentioned already that the monograph on 

 Antedon rosacea which is the subject of this notice is a part 

 of Messrs. Vogt and Yung's ' Traits d' Anatomic Comparee 

 Pratique,' and one would therefore expect to find some notice 

 in it of the comparative morphology of the Echinoderm 

 skeleton. The homology of the basal and radial plates of a 

 Crinoid with the genital and ocular plates of an Echinid is 

 now universally acknowledged ; but though Vogt and Yung 

 make plenty of comparisons between the vascular system of 

 Crinoids and those of other Ecliinodcrms, they make no refer- 

 ence whatever to the morphology of the apical system, a point 

 about which there is a much more general consensus of opinion 

 than exists about the vascular system. They give a very 

 good figure of the apical plates of an Urchin, but say not a 

 word respecting their homology with the basals and radials 

 of a Crinoid. In fact they make no reference whatever to the 

 former, which is a somewhat singular omission, considering 

 their morphological importance in the organization of the 

 Crinoid type. The authors do, it is true, speak of the cirrus- 

 vessels as separating from one another " pour se continuer, a 



* " Anatomie und Schizogonie der Ophiadis virens, Sars," Zeitscbr. f. 

 wiss. Zool. 1876, Bd.xxvii. p. 440, Taf.xxxii. tigs. lo-17, 20, 21, Taf. xxxiii. 

 fig. 30. 



