REPORT ON THE CRINOIDEA. 19 



have many sections through the calyx, both of Antedon rosacea and of other species of 

 Cornatulae in which there is no trace of them. Three such undamaged sections are 

 figured in my Actinometra-memoir, 1 and I certainly never expected to find an accidental 

 fracture in the skeletal tissue outside the central capsule described as a part of the 

 chambered organ, the cavities of which are entirely within this capsule, as explained above. 



If there really be such a diverticulum of the body-cavity within the calcareous 

 substance of the centro-dorsal piece as is described by Vogt and Yung, i.e., between its 

 inner floor on which the central capsule rests and its external surface, its presence could 

 easily be demonstrated by rubbing away the outer surface of the centro-dorsal until this 

 cavity was reached ; and I would commend this method of proving the accuracy of their 

 anatomical descriptions to the attention of Messrs. Vogt and Yung. They have made a 

 precisely similar error in their description of the anatomy of the arms, figuring a large 

 rent in the skeletal tissue of an arm-joint as the " cavite de la syzygie." They will not 

 find this cavity if they will take the trouble to rub away the syzygial surface of an arm- 

 joint, which contains but one cavity, that of the axial canal. 



Another extraordinary blunder which is committed by these authors in the 

 explanation of fig. 276 is their description of the fibres (b) which unite the first radials 

 to the centro-dorsal as the " muscles entre le premier et le second radial." Their mono- 

 graph contains many other errors of a similar kind, not only in their interpretation of 

 well-known anatomical facts, as in this last case, which they might have avoided by 

 consulting the works of their predecessors, but also misrepresentations of passages in 

 these writings. These, however, are more fitly dealt with elsewhere. 2 



C. The Rosette. 



While the presence of a cirrus-bearing top stem-joint or centro-dorsal piece is common 

 to all Cornatulae, even including the aberrant Thaumatocrinus, this genus, together with 

 Atelecrinus (PI. VI. figs. 5, 7) and many fossil species, differs from the adult condition 

 of all other recent Comatulas in the presence of the basals on the exterior of the calyx. 



It was for a long time supposed that the basals of other Crinoids were unrepresented 

 in recent Comatulse ; but their existence in the Pentacrinoid larva was eventually recog- 

 nised by Allman, Sir Wyville Thomson, and Dr. Carpenter ; and the last-mentioned 

 observer discovered the remarkable changes which they undergo during the later part 

 of Pentacrinoid life. These changes result in their transformation into the "rosette" 

 which lies close to the dorsal surface of the central funnel within the radials, and covers 

 in the upper opening of the centro-dorsal cavity that lodges the chambered organ (sensu 

 stricto). It is well seen in the figures of Antedon eschrichti, Antedon accela, Antedon 



1 Trans. Linn. Soc. Lond. (Zool.), 1879, ser. 2, vol. ii. pi. viii. figs. 3, 4, 7. 



2 The Morphology of Antedon rosacea, Ami. and Mag. Nat. Hist^ 1887, ser. 5, vol. xix. pp. 19-41. 



