70 
THE YOYAGE OF H.M.S. CHALLENGER. 
turned inward to the disk. Fig. 15 has, besides the main aperture, two other apertures, 
small orifice ( z ), and a remarkable triradiate fissure (y) ; the smaller cyst shows only one 
secondary aperture on the place where in fig. 15 C the fissure y is visible. The cyst 
(fig. 15), in spite of its large size, contained only a single pair of the parasites, but both 
were of a larger size than usual, the female 4 mm., the male 2 mm. in length ; both were 
of a deep brown colour. 
A single specimen, which had been mounted on a slide by Dr. v. Willemoes Suhm, 
and which was sent me by Mr. Murray, contained a male. It was labelled — “ Myzostoma. 
The little individual of the parasite pair in the cavity of the Comatula arm.” There were 
no remarks as to locality, but undoubtedly a passage from the third letter of v. Willemoes 
Suhm 1 refers to this species, since he, as is evident from his preparations, has not sepa- 
rated Myzostoma tenuispinum from the following species Myzostoma willemoesii. 
Hosts. — All the cysts collected during the Challenger Expedition were found, upon the 
following hosts : — 
(a) Antedon incequalis , P. H. C. (No. 62), Station 170 (Kermadec Islands). 
Two out of twelve specimens had cysts. One had four (two small and 
two larger), the other five (two small and three large ones), all in the 
first third of the arm. Station 174 (south-west of the Fiji Islands). — 
One out of five individuals had cysts (among them the compound cyst 
referred to of Myzostoma tenuispinum and Myzostoma willemoesii). 
(b) Antedon angusticalyx, P. H. C., from Station 214 (south-east of the Philip- 
pine Isles). One specimen had three large cysts ; there were also two 
arms, each from a different individual, and both furnished with a large 
cyst on its basal part (fig. 15) ; and two fragments each with one cyst. 
(c) Antedon basicurva, P. H. C. (No. 61), from Station 170 (Kermadec 
Islands). One specimen (out of fourteen) had a single cyst (formed 
as fig. 6) in the proximal third of the arm. As I could not extend 
the arms of the Crinoid, which were strongly folded together, it is very 
possible that other cysts, though present, had escaped my attention. 
(d) Antedon incisa,V. H. C. (No. 61a), from Station 170 (Kermadec Islands). 
There was a single cyst on one out of five individuals on the proximal 
third of the arm. Fig. 16 shows it twice the natural size (copied from 
P. H. Carpenter’s plates). Station 174 (south-west of the Fiji Islands). 
— Two specimens of the Crinoid were dredged, but neither had cysts. 
1 Yon der Challenger Expedition, Brief III., Zeitschr. f. wiss. Zool., Bd. xxv., 1875, p. xxxi. : “Den kleinen 
Parasiten der Comatula, Myzostomum, fanden wir zuerst in Halifax und seitdem habe ich ihn oft bemerkt. Diesmal 
(i.e., between Kermandek and Fidji Islands) aber unter eigenthiimlichen Umstanden unter denen er wohl noch nicht 
zur Beobachtung gekommen ist. Ich fand niimlich an den Armen einer Comatula aus 600 Faden Anschwellungen 
von der Grbsse eines Schrotkomes No. 3. Eine kleine Offnung fiihrte ins Innere, das von einer zarten Haut ausge- 
kleidet war, und hier fanden sich stets 2 Myzostomen, ein grosses Individuum, das viel dicker ist als irgend welche, die 
ich friiber frei auf den Armen des Seestems fand, und ein kleineres, das etwa nur ein Funftel des vorigen misst.” 
