74 
THE VOYAGE OF H.M.S. CHALLENGER. 
(fig. 2, C), and had a small aperture at the outer end. The most remarkable thing about this 
cyst was that, although undivided by any septum, it contained two pairs of Myzostoma 
inflator, which were closely pressed together and filled up the whole of the interior of the 
cyst. One pair was larger than the other, the female measuring 2 - 2 mm. in length by 
1 '2 mm. in breadth, and the male (fig. 4) '9 mm. in length by ‘8 mm. in breadth. 
The relative length as well as the form of the hooks was the same in both sexes as in 
Myzostoma murrayi from Antedon radiospina. 
Hosts. — (a) Antedon angustiradia, P. H. C., from Station 192 (south-west of Papua) 
of the Challenger Expedition. 
( b ) Actinometra pulchella, Pourt., sp., from Station 294 (Barbados) of the 
“ Blake ” Expedition. 
67. Myzostoma murrayi, n. sp. (PI. XV. figs. 5-13). 
I found the peculiar cysts of this species first upon Antedon duplex, P. H. C., from 
St. Vincent (Station 269 of the “Blake” Expedition). There were upon the disk of this 
crinoid, quite close to the mouth, two club-shaped cysts, shown diagrammatically in fig. 8. 
The free end of the cyst projects between the arms on the dorsal side; -the extremity is 
considerably thicker than the rest and bears an aperture. The larger of the two cysts 
measured 3 ’5 mm. long with a greatest diameter of ’86 mm., the width of the aperture 
being T8 mm.; it was hanging down quite freely, whereas the smaller cyst was attached 
firmly to the disk for its whole length. The border of the cyst was tubercular, 
appearing to consist of numerous single calcareous plates united together by the solid 
membrane which lines the interior of the cyst. I had considerable difficulty in extracting 
the inhabitants of the cysts, and indeed only succeeded in getting some fragments from 
the larger one, since the parasites were very closely pressed into the various folds and 
furrows upon the inside of the cyst. 
Mr. Carpenter, however, sent me a specimen of Antedon radiospina (Station 170, 
Challenger Expedition) containing two cysts of much larger size than the others. The 
first of these projected outwards and upwards from the ambulacral furrow at about the 
middle of the length of the arm ; the second cyst was somewhat larger, placed in the 
same position on its host as the specimen from the “ Blake” Expedition. This latter cyst 
is shown in fig. 9, C, magnified seven times; its length was 8 mm. Both these cysts were 
slightly connected along their whole length with the skin of the host. When the cyst was 
cut open lengthways, it was found to contain a female (fig. 10, $ ) which filled the distal 
two-thirds of the cyst, its dorsal surface being bent inwards ; between the ventral 
surface of the female and the wall of the cyst, near the orifice, was a dwarf male ($)] 
the diameter of the body of the female, circular when fully stretched out, was 5 ’5 mm., its 
greatest thickness rather more than - 5 mm. ; the whole body becomes thinner towards the 
margin, but is transparent throughout, and of a brownish colour. There was no trace of 
