IN THE MOEPHOLOGT OF THE CYSTIDEA. 45 



written had the author got up his subject better ; and yet the 

 literature, while by no means extensive, is easily accessible. 



The worst offender, however, in this respect is Neviani, who 

 seems to be altogether unacquainted with any of the results arrived 

 at by the reporters on the Echiuoderms of the ' Challenger ' and 

 ' Blake ' expeditions, and also with the palteontological work of 

 Messrs. Wachsmuth and Springer. Hyponome Sarsii, the sup- 

 posed recent Cystideau from Cape York, was shown in 1879 to 

 be merely the detached disk of an Antedon * ; and it was with 

 some surprise that I found it mentioned by Neviani in his recently 

 published article on the Phylogeny of Echiuoderms f? which is 

 so much behind the times that no further reference need be made 

 to it. 



2. The Water-vascular System and its delations. 



In a preliminary note to his forthcoming Morphological Studies 

 on Echiuoderms, Cueuot makes no reference to his former view 

 of the " ovoid gland " as a i'actory of amcebocytes ; but regards 

 it as an organ of respiration and excretion, functions which may 

 be shared by the water-vascular system, with which it is always 

 more or less intimately associated $. Perrier, however, continues 

 to maintain its plastidogenic functions : — 



" Chez les Stellerides, Ophiurides, et Echinides, I'appareil ambulaeraire est 

 accompagne par Vappareil flasticlogene, qui en reproduit toutes les dispositions 

 esseutielles. Get appareil comprend un corps ^plastklogene, qui accompagne la 

 tube bydrophore; un anneau 'plastidoghia on anneau de Tiedemann, presque 

 contigu a I'anneau ambulaeraire ; cinq f aisceaux de tubes plastidogenes ou tubes de 

 Ludwig, qui suivent le trajet des tubes ambulacraires "§. ] 



These " tubes plastidogenes " have been often described as 

 blood-vessels, though Perrier refused to accord them this rank. 

 I am glad to learn, however, that he admits their existence, which 

 has been frequently denied. Like Durham, I prefer to distin- 

 guish the radial portions of the plastidogenic apparatus as the 



* " Preliminary Eeport upontbeComatulseof the 'Challenger' Expedition." 

 Proc. Eoy. Soc. 1879, vol. xxviii. p. 388 ; and also Quart. Journ. Micr. Sci. 

 vol. xix. 1879, pp. 14,30. 



t "Appunti suUa fillogenesi degli Echinodermi," Eivista Italiana di Scieuze 

 Naturali, Ann. xi. 1891, fasc. 2, p. 6 of separate copy. 



\ "Etudes morphologiques sur les Echinodermes. Note preliminaire." Arch 

 Zool. Exp. et Gen. 2nie serie, tome xix. 1891, p. xiii. 



§ Biblioth. Ecole d. hautes Etudes, Sci. Nat. tomexxxiv. 1888, Article No. 4, 

 p. 71. 



