134 THE VOYAGE OF H.M.S. CHALLENGER. 
species of Cirripedes are also frequently met with on the stems and cirri of Pentacrinide 
(PL LIL fig. 1), both im the Caribbean Sea and in the East Indian Archipelago. Thus, 
for example, Scalpellum album is common on the stem and cirri of many individuals of 
Metacrinus dredged off the Ki Islands (Station 192), while Scalpellum balanoides and also 
Verruca nitida occur attached both to Pentacrinus and Metacrinus from off the Meangis 
Islands (Station 214). At this last Station too, an obscure larval Cirripede occurred, 
attached to a cirrus of Metacrinus varians by its ventral margin, while a minute Avicula 
was anchored by a few threads to a cirrus of Metacrinus interruptus at Station 209. 
Von. Graff has described a small Stylina* as parasitic on the anal tube or pinnules of Antedon 
rosacea, and found that holes remained after its removal. hizocrinus lofotensis in like 
manner is often infested with two or three small shells of Stylifer which bore comparatively 
large holes in its calyx. Pourtalés has described some examples of this species from the 
Florida Channel as having the calyx and part of the stem coated with an encrusting 
Hydroid polype ; and some small Rhizopods are shown in PI. X. fig. 16 on the stem 
of a Rhizocrinus rawsont from the Azores. I have found Yrunecatulina lobatula to 
be abundant on the cirri of the Comatulee which were obtained by the Dutch Arctic 
Expedition in the Barents and Kara Seas; while Polytrema miniacewm is common on 
the stem and cirri of the Pentacrinidee dredged at Stations 192 and 214. 
The especial parasite of the Crinoids, however, is the well-known Myzostoma,? which 
is sometimes found infesting them in great numbers. I have myself removed five 
moderately large specimens from a single individual of a Bathycrinus aldrichianus, and 
as this had been some years"in spirit before reaching me, it may very likely have served 
as host to a still larger number; while in the Mediterranean twenty-seven have been found 
infesting a single Comatula. They attach themselves to the stem, disk, and arms, either 
on the ventral or on the dorsal surface. Iam not aware that they have ever been met 
with on Rhizocrinus, which often supports boring Stylifers ; but v. Willemoes Suhm found 
them on Hyocrinus, Bathycrinus, and on many Comatule, though he did not meet with 
free Myzostomida on any of the Challenger Pentacrinide. A closer examination, 
however, has revealed their presence in a few cases. The abnormal specimen of 
Metacrinus angulatus from the Ki Islands (Station 192), which is figured on Pl. XX XIX. 
fig. 2, had a Myzostoma wyville-thomsoni resting between the ordinary anal tube and 
the second smaller one at its side. In many cases the Myzostoma, instead of living in the 
free state, causes an abnormal growth of the calcareous tissue of the arm so as to form a cyst 
in which two or three individuals live. At two Stations in the South, and at another in 
the North Pacific, these cysts proved to be tolerably common. At the first named 
(Nos. 170 and 174) the cysts were limited to the arms of four Comatule; while at 
1 Stylina comatulicola, ein neuer Schmarotzer der Comatula mediterranea, Zeitschr. f. wiss. Zool., 1875, Bd. xxv., 
Suppl., pp. 124-126. 
2 For a full account of the Myzostomida, see Prof. L. v. Graff, Das Genus Myzostomum, and Zool. Chall. Exp., 
part xxvii., 1884. 
ie 
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