C U.XM'h'imm S DIOMED 1 67 



Embryology of Echinoderms, both published in L864, though he quotes 

 the title of the lasl memoir; for he makes do allusion to m\ description 

 of the central anal plate in young Echinoids in L 864, except in connection 

 wiili my paper on the young stages of Sea-urchins in the Preliminary Im- 

 port on the Echini dredged bj Mr. Pourtales* between Florida and Cuba. 

 Nor does Love'n, while discussing the homologies of the dorsal plates <>i 

 several young stages of Asterias glacialis, refer in an\ way to the descrip- 

 tions and figures given in the " Erubryolog} of the Starfish " of the early 

 stages of Asteracanthion. 



In 1ST'-' Beyrichf concludes an article on the basis of the Crinoidea 

 brachiata with suggestions on the analogies of the peculiar subdivision of 

 the basis of the Crinoids and the symmetrical structure of other Echi- 

 noderms, especially Sea-urchins. He says the radials and interradials of 

 Crinoids correspond to the ambulacra and interambulacra of the Sea- 

 urchins, and. further, that the radials of Sea-urchins, as in the Crinoids, do 

 not unite at the dorsal pole, but are separated by the apical system (Schei- 

 telapparat), which from its position is analogous to the basis of the Crinoids. 

 He also calls attention to the fact that in the symmetrical Sea-urchins one 

 of the interradials is specialized above the others by the presence of the 

 anus, dividing the test symmetrically by an anal axis, as in the Crinoids. 

 lie also says that in the composition of the apical system of the Sea-urchins 

 we find no analogue to the deviation of the regular pentagonal subdivision 

 of the basis of the Crinoids. 



Midler in 1854 also already foreshadows the apical homologies of the 

 Echinoderms. He says: " Der Kelch eines . . . Echinosphasrites, Echinoen- 

 crinus sei der Apex eines Seeigels, er ist jedoch eine solche Ausdehnung 

 des Apex, welche die s'ammtlichen Eingeweide des Thiers umfasst." | 



In the comparison which I made between the plates of the young Star- 

 fish and those of a Crinoid, I spoke of the central plate as present in both, 

 and called attention to the absence of homology between plates which 

 constitute the bulk of the apical system in the young stages of the Star- 

 fish and Crinoid, homologizing the genitals of the young Starfish (the 

 interradials,§ as I called them) with the basals of Allman's Antedon stage. 



* Bull. Mus. Comp. Zool., Vol. I. No. 9, 1869. 



t Monatsber. d. K. Akad. d. Wiss. Berlin, Feb. 9, 1871, p. 54. 



% Mtiller, Ban der Echinodermen, 1854, p. 14. 



§ But I had no intention of comparing them to what have been called interradials or calyx inter- 

 radials in paleozoic Crinoids. I merely intended to state that they were plates having an interradial 

 position. 



