78 CATALOGUE OF THE BLASTOIDEA. 



there was an injecting apparatus beneath each ambulacrum of a Blastoid capable of 

 moving fifty pairs of pinnules, each composed of a more or less double row of calca- 

 reous joints. On the other hand, some recent Crinoids have over one hundred arms, 

 each composed of 100-150 joints, with a pinnule on every one. With a few exceptions, 

 every arm-joint and every pinnule-joint is united to those before and behind it by a 

 pair of muscular bundles. Is not this a muscular system vastly more complex than 

 any Blastoid could have ever possessed ] 



This theory of White's has not met with any acceptance among naturalists for the 

 reason already mentioned. It has never been seriously discussed, and has gradually 

 passed into oblivion, so that there is no need to refer to it any further. 



The case is different, however, with Messrs. Dujardin and Hupe 1 , whose remarks 

 on the hydrospires, although short, are very much to the point. They were the 

 first to recognize that the interambulacral hydrospire-slits of Cadaster lead into 

 lamellar tubes resembling those which lie beneath the ambulacra of Pentrcmites ; 

 and like both McCoy and Hall they compared this system to the pectinated rhombs 

 of the Cystids, which were then gradually coming to be regarded as respiratory in 

 function. " Ces lames, ou ces canaux lamellaires, quand ils sont tout-a-fait internes, 

 recoivent le liquide exterieur par les pores des ambulacres, et Ton peut penser que 

 le double orifice qui termine chaque ambulacre vers le centre des Pentrcmites, est 

 destine a la sortie de l'eau qui a servi a la respiration." We are strongly inclined to 

 think that the view taken by Dujardin and Hupe concerning the relation between 

 the hydrospire-pores and the summit-openings is the true one, the former being 

 afferent, and the latter efferent ; and for this reason we think it all the more likely 

 that the summit-openings also served for the discharge of the genital products as 

 supposed by Say, Roemer, and others. Dujardin and Hupe, however, not only 

 abandoned this view as improbable and incorrect, but they attributed a genital function 

 to the lateral opening which had been generally described as the anus 2 , and was 

 supposed to be oro-anal by White. In this step we cannot follow them, but 

 fchey are certainly entitled to the credit of being, so far as we know, the first 

 writers to give a rational explanation of the function of the hydrospires as respiratory 

 organs. 



Their remarks appear to have been unknown to Rofe 3 , who obtained vertical 

 sections of the hydrospires in Pentremites, Granatocrinus, and Cadaster, and was the 

 first to demonstrate the connection of the pores at the sides of the ambulacra with 

 the tubular apparatus beneath them ; but the absence of these pores in the last 

 named genus seems to have puzzled him. His sections, however, enabled him to 



1 Hist. Nat. des Xoophj-tes Eehinodermcs, Paris, 1802, p. 88. 



- Ibid. pp. 88, 89. 



3 Geol. Mag. L865, pp. 249-251. 



