110 Dr. P. H. Carpenter on some Points iyi 



belween the two types is in the number of their radials. 

 What would he think of the reviewer of his Report on the 

 ' Blake ' Starfishes who said that the only difference between 

 his two genera Hymenodiscus and Antheno'ides was that the 

 latter had but five arms and the former twelve ? 



Prof. Perrier's investigations into the obscure and much- 

 neglected subject of the physiology of the Crinoids have led 

 him to attribute a hitherto unsuspected function to the syzy- 

 gial unions which occur in certain portions of the skeleton. 

 He tells us* : — " H y a au niveau de ces sortes d' articulations 

 immobiles qu'on appelle les syzygies, chez les Encrines, tout 

 un syst^me de cavit^s puissamment munies des muscles qui 

 chassent ^videmment I'eau dans la substance m^me du tissu 

 impr^gne de calcaire des bras ou la conduisent au dehors et 

 I'expulsent par les trous qui sont repartis a egale distance sur 

 le pourtour de la syzygie." 



It is, I think, much to be regretted that Prof. Perrier should 

 have departed so far from the nomenclature of Miiller and 

 his successors as to speak of a syzygy as a kind of immovable 

 articulation. Miillerf called it an " unbewegliche Nathverbin- 

 dung ;" and he distinguished between a " Nath " and a 

 " Gelenk " in the anatomy of a Crinoid. He only used the 

 latter term when the two articulated joints were capable of 

 movement upon one another; and this distinction has been 

 almost universally adopted by later writers upon the subject, 

 so that the term " articulation immobile," which Prof. 

 Perrier employs has a somewhat contradictory sound. In 

 the next line we are told by Prof. Perrier that among the 

 " Encrines," the term which he uses throughout the whole of 

 this article for the Stalked Crinoids only, the two joints are 

 separated by a system of cavities which open externally by a 

 series of pores round the edge of the syzygy. Such being 

 Prof. Perrier's statement, let us examine in detail the evidence 

 upon which it is based. In the first place, as explained in 

 the ' Challenger ' Report |, there are no syzygies at all any- 

 where in the arms of Batliycrinus. The Crinoids of this type 

 are consequently very far from possessing such an extensive 

 communication between the internal cavity and the exterior 

 as is supposed by Prof. Perrier's theory that they are really 

 in the same physiological condition as the sponges. For the 

 number of ciliated water-pores on the disc of Bathycrinus 

 is extremely limited and by no means a " foule d'orifices ;" 



* < Revue Scientifique,' May 30, 1885, p. 692, note. 

 t " Ueber den Bau des Pentacnnus caput-medustp/' Abliaudl. d. k. 

 Akad. d. Wiss. Berlin, 1843, p. 39 (of separate copv). 

 X Zool. Chall. Exp. part xxxii. pp. 9, 231-233. 



