REPOET ON THE MYZOSTOMIDA. 
73 
Host . — All the cysts were collected during the Challenger Expedition, and found on 
the following species of Crinoids : — 
(a) Antedon basicurva, P. H. C. (No. 61), from Station 170 (Kermadec 
Islands). One individual had a single cyst on the proximal fifth of the 
arm. Another specimen out of the fourteen had a cyst of Myzostoma 
tenuispinum. 
(b) Antedon incequalis, P. H. C. (No. 62). Station 170 (Kermadec Islands). 
The specimen having four cysts of Myzostoma tenuispinum, had also 
one pinnule malformed by Myzostoma willemoesii. Station 174 (south- 
west of the Fiji Islands). A specimen with cysts of Myzostoma 
tenuispinum and also a combined cyst of this species and Myzostoma 
willemoesii. 
66. Myzostoma infiator, n. sp. (PI XV. figs. 1-4). 
Fig. 1 represents a specimen of Antedon angustiradia, bearing at the commencement 
of two of the arms the cysts of this species. The cysts are pear-shaped, the thicker end 
being turned towards the disk and the thinner end being attached near the ambulacral 
furrow of the arms. The length of each cyst is about 3 mm., and they are connected 
with the arm along their whole length by a transparent delicate membrane. The wall 
of the cysts is hard and calcareous. In each cyst is a larger female individual 
and a smaller male, not unlike Myzostoma murrayi; in neither are the cirri or the 
suckers developed, and the female has no parapodia. From the ojaening of the cyst A 
the female projected slightly. In spite of its similarity to Myzostoma murrayi this species 
is evidently distinct ; the female has a diameter about onc-third less than the length ; 
its contour is somewhat oblong, and the walls of the body are thin and delicate, so 
as to permit of the numerous intestinal caeca (fig. 3) and the ova being distinguished from 
the outside. The male (fig. 4) is provided like the female with a terminal mouth and 
anal aperture, and is similar in form. It differs from Myzostoma murrayi, not only in the 
structure of the intestinal canal, but also in the character of the testes, which are ramified 
through the whole body, after the manner of the free-living species, instead of being 
concentrated into a rounded and compact organ, as in Myzostoma murrayi and other 
cysticolous species ; the genital openings also are not marginal but seem to be on the 
ventral side and further inwards than usual. I am unable to make any more exact state- 
ments, since the lateral portion of the specimen was rather injured, and also somewhat 
bent towards the ventral side. Some other specimens, from an Actinometra dredged at 
Barbados (Station 294 of the “ Blake ” Expedition), were in a better condition for 
examination. The cyst here was sausage-shaped, extending in a radial direction from 
the mouth to the border of the disk, about 3 mm. in length, and with a hard, rough 
wall. It was completely fused with the disk of its host throughout its whole extent 
(zool. CHALL. EXP. PART XXVII. — 1884.) Del 10 
