NOTES ON EOHINODERM MORPHOLOGY. 311 



Am phi ura, as well as those corresponding to the basals (3). 

 Fewkes 1 thinks, however, that it would have been better " in 

 considering the relationship of the basals in the young 

 Amphiura and their homologues in the projection of the calyx 

 of an Antedon larva " if I had copied Ludwig's fig. 25 

 instead of his fig. 24, i. e. that showing the monocyclic and not 

 the dicyclic stage of Amphiura. It is curious that he fails 

 to see the reason why I copied the figure of the older, in pre- 

 ference to that of the younger stage. Homologues of the 

 Crinoidal basals had long been recognised in the so-called 

 genital plates of Urchins and Starfishes. But up to the time 

 of the publication of Ludwig's memoir, representatives of the 

 under-basals of a Crinoid 2 were not known to exist in any of the 

 Echinozoa ; and it was for the purpose of demonstrating their 

 presence in Amphiura that I copied the figure of the older 

 and dicyclic condition rather than that of the younger and 

 monocyclic one, with the remark, 3 " The plates in the outer 

 ring (fig. ii, 3) are inter-radial, while those of the inner ring 

 next the dorso-central are radial in position (fig. n, 2). In 

 these plates we have, I believe, the representatives of the 

 diycyclic base of Marsupites and other Crinoids, viz. a 

 proximal ring of under-basals hitherto unknown in any of the 

 Echinozoa, and a distal ring of interradial plates correspond- 

 ing to the basals of the Crinoid and the genitals of the Asterid 

 or Urchin, which have not been previously discovered in an 

 Ophiurid." 



The doubts which seem to have occurred to Fewkes respect- 

 ing the homologies of the adaxial ring of interradial plates in 



1 Loc. cit., p. 129. 



2 While this paper was in the press an important discovery was announced 

 by Mr. H. Bury at the Manchester meeting of the British Association. He 

 has found under-basals in the ciliated larva of Antedon rosacea; but they 

 soon fuse with the top stem -joint (centro-dorsal), and all trace of them is 

 lost when the cirri appear. This is a very striking confirmation of the views 

 of Messrs. Wachsmuth and Springer, whose palseontological studies had led 

 them to express the belief that under-basals might be present in the early 

 larva of Comatulse. 



3 'Quart. Journ. Micr. Sci.,' 1882, vol. xxii, New Ser., p. 380. 



