210 THE VOYAGE OF H.M.S. CHALLENGER. 
than is usually 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. Ve. fig. 1, 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. Ve. fig. 2, ov). The ova, of which all stages are visible, are more like those of 
Antedon eschrichti than is the case in many Comatule, 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 with regard to the 
presence of a radial nerve and blood-vessel, which are ordinarily found between the 
water-vessel and the ciliated epithelium of the food-groove, but thisis 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 Holopus; and I see no good 
reason to believe that in any essential point of its visceral anatomy there is any important 
difference between it and other Crinoids. 
All the specimens of Holopus 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, off Montserrat, the “ Blake” dredged an imperfect whitish specimen. This 
consisted of a detached axillary jot and the two arms belonging to it, as shown in 
Pls. 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 Pentacrinide. 
Prof. Moseley informs me that many of the individuals dredged by the Challenger 
were white when captured, although tinged with pentacrinin, 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 St Rawson Rawson, 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, 
