134 THE VOYAGE OF H.M.S. CHALLENGER. 



species of Cirripedes are also frequently met with ou the stems aud cirri of Pentacriuidse 

 (PI. LII. fig. l), both in the Caribbean Sea and in the East Indian Archipelago. Thus, 

 for example, Scalpellum album is common on the stem and ciiTi of many individuals of 

 3Ietacrinus dredged off the Ki Islands (Station 192), while Scalpellum halanoides and also 

 Veri^uca nitida occur attached both to Pcntacrinus and Metacrinus hora. off the Meangis 

 Islands (Station 214). At this last Station too, an obscure larval Cirripede occurred, 

 attached to a cirrus of Metacnnus varians by its ventral margin, while a minute Avicula 

 was anchored by a few threads to a cirrus of Metacrinus interruptus at Station 209. 

 Yon. Graff has described a small Stylina} as parasitic on the anal tube or pinnules oiAntedon 

 rosacea, and found that holes remained after its removal. Rhizocrbms lofotensis in like 

 manner is often infested with two or three small shells of Stylifer which bore comparatively 

 large holes in its calyx. Pourtales has desci-ibed 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 Ehizopods are shown in PL X. fig. 16 on the stem 

 of a Rhizocrinus rawsoni from the Azores. I have found Truncatidina lobatula to 

 be abundant on the cirri of the Comatulaj which were obtained by the Dutch Arctic 

 Expedition in the Barents and Kara Seas ; while Poli/trema miniaceum is common on 

 the stem and cirri of the Pentacrinidse 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. I am 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 Comatulse, though he did not meet -nith 

 free Myzostomida on any of the Challenger Pentacrinidse. 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 XXXIX. 

 fig. 2, had a Myzostoma ivyville-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 w^hich 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 Comatulse ; while at 



1 Stylina comatulicola, ein neuer Schmarotzer der Comatula mediterranea, Zeiischr.f. iciss. Zool, 1875, Bd. sxv., 

 Suppl., pp. 124-126. 



* For a fuU account of the Myzostomida, see Prof. L. v. Graff, Das Genus Myzostomum, and Zool. Cball. Exp., 

 jjart xxvii., 1884. 



