MONOGRAPH OF THE EXISTING CEINOIDS. 675 



not possible to determine the genus to which Tcenia mysostoma belongs, but that 

 presumably it is the larval stage of a fish tapeworm. Various genera are repre- 

 sented among the tapeworms of fishes, but very little is known of their larval 

 stages. 



Wheeler has described a distome, Distoma myzostomatis, from Myzostomum 

 platypus a curious instance of a trematode parasitic within a myzostome, which 

 itself is parasitic within a crinoid. 



Wheeler has also described Amoeba mysostomatis, possibly, as he suggests, the 

 young of some gregarine, which he found in great numbers in the body cavity 

 of Myzostomum parasiticum, where it attacks the ova. 



The two following cases of parasitism among the ophiurans are of interest in 

 connection with the worm parasites of the crinoids. 



Metschnikoff has described a curious worm, Rhopalura, of the family Ortho- 

 nectidae, the cysts of which sometimes fill the body cavity of Amphiura squamata 

 Sars and take the place of the ovaries, which disappear. 



Ludwig has called attention to an extraordinary polychsete which he called 

 Ophiuricola cynips and which he found in the body of a specimen of OpTiioglypha 

 tumulosa Liitken and Mortensen from 2,845 fathoms (5,203 meters). 



None of the turbellarians have been found associated with the crinoids, though 

 Anoplodium occurs within or upon holothurians. 



UNDETERMINED WORM. 



In some sections of three different specimens of Comanthus parvicitTa which 

 had been brought back from the Philippine Islands by Professor Semper, which 

 he prepared while studying at the zoological laboratory of the University of 

 Wiirzburg, P. H. Carpenter found a peculiar worm. 



It was first noticed in the cceliac canal of the arms, which it often almost filled, 

 so as to suggest the idea that the egg had been introduced into the body cavity and 

 had developed in that part of it. He subsequently found it in the visceral mass 

 of two other individuals, occupying some of the meshes in the connective tissue 

 network which fills up the intervisceral ccelome. 



PARASITE OF DOUBTFUL AFFINITIES. 



In Notocrinus vinlis Dr. Th. Mortensen found a small elongate body lying 

 in the cavity of the ovary, which was evidently a parasitic organism. Having 

 been unable to find another specimen of this parasite he did not venture to state 

 definitely what it was, but suggested that it might have been a myzostome. 



CCELENTERATA. 



In 1868 Count Pourtales mentioned that the columns of Bourgueticrinus 

 hotessieri (Bythocrinus, sp.) which he was recording from 237, 248, and 306 

 fathoms off the Samboes and off Sand Key, Florida, were covered with a thick 

 brown deciduous skin. He later discovered that this supposed skin was a parasitic 

 growth of a hydroid polyp. 



