210 THE VOYAGE OF H.M.S. CHALLENGEE. 



than is usuallj^ the case so near the disk. It is connected with ovaries alternately on 

 opposite sides of the arm, from about the first to the fifteenth brachial (PL Vc. fig. l,gc.). 

 The ovaries are short and stout, and confined to the pinnule-bases in the broader, lower 

 parts of the arms; but where the joints are smaller the ovaries appear immediately beneath 

 the water-vessel, and the boundaries between the three arm-canals cannot be traced 

 (PL Vc. fig. 2, ov). The ova, of which all stages are visible, are more like those of 

 Antedon eschrichti than is the case in many Comatulse, but they are somewhat larger, 

 reaching a diameter of 0'22 mm.; while 0"1737 mm. is the size of the largest ovum of 

 Antedon eschrichti which was measured by Ludwig. 



I have unfortunately been unable to make out anything definite wdth regard to the 

 presence of a radial nerve and l)lood-vessel, which are ordinarily found between the 

 water-vessel and the ciliated epithelium of the food-groove, but this is so often the case in 

 other Crinoids, except in sections of more than average goodness, that I have no doubt 

 whatever respecting the existence of these structures in Ilolojnis ; and I see no good 

 reason to believe that in any essential point of its visceral anatomy there is any important 

 difi'erence between it and other Crinoids. 



All the specimens of Holojnts which have been preserved in the dry state are of a 

 dull dark green tint, sometimes verging on black. But Mr. Agassiz records that on one 

 occasion, ofi" Montserrat, the " Blake " dredged an imperfect whitish specimen. This 

 consisted of a detached axillary joint and the two arms belonging to it, as shown in 

 Pis. Va. fig. 3, and Vb. fig. 4. The green colour assumed by the dry specimens is 

 possibly due to post-mortem changes, as seems also to be the case in the Pentacrinidee. 

 Prof. Moseley informs me that many of the individuals dredged by the Challenger 

 were white when captured, although tinged with pentacriniu, owing to the colouring 

 matter being in some way masked during life, and only manifesting itself after death. 

 During a visit which I paid him recently at Oxford, one of the dry specimens of Holopus 

 was treated with spirit, and yielded a dull green solution with a red fluorescence. 



Prof. Moseley examined it with the spectroscope, and found the colouring matter to 

 be identical with the pentacrinin which he had discovered in the various species of 

 Pentacrinus and Metacrinus that were dredged by the Challenger in the Pacific and 

 East Indian Archipelago. 



Holopus has not yet been met with outside the Caribbean Sea. D'Orbigny's original 

 specimen was obtained at Martinique, while, thanks to Sir Rawson Raw^son, others have 

 been discovered in the neighbourhood of Barbados. The young individual figured 

 in PL V. was dredged by the "Blake" in 100 fathoms off" Bahia Honda; while 

 the white fragment, already mentioned, was found at a depth of 120 fathoms off" 

 Montserrat. 



During the stay of the Challenger at Bermuda,^ Sir Wyville Thomson obtained from 



1 The Atlantic, vol. i. p. 321. 



