282 DISCOVERY REPORTS 



gonad, and only one or two gonads to each side of the arm. In adult specimens there 

 are several more, up to about eight to ten eggs in each gonad (I have found no adult 

 specimen with embryos, only with eggs). The eggs are large, rich in yolk ; in the young 

 embryonal stages there is a very distinct whitish animal pole and a large, yellowish-brown 

 vegetative pole, which latter in the course of further development is enclosed by the dorsal 

 skin of the embryo. Such embryos have a curious appearance, for the arms look like 

 small, fat sausages, with the skeletal rudiments very small in comparison with the 

 thickness of the arm. A careful study of the development of this species would clearly 

 be remunerative ; I have, however, neither the material nor the time to undertake such 

 a study. 



One of the specimens (St. WS 33) is infested by & parasitic Gastropod; it lies wholly 

 within the body of the Ophiuran, a small opening in one of the ventral interradii showing 

 the place through which the parasite entered. The body of the parasite is wholly sac- 

 shaped, without any trace of its shell left, and it would, indeed, be impossible to tell 

 what kind of animal it was, were it not that it is filled with young 

 embryos with a well-developed, typical Gastropod shell (Fig. 19). These 

 young snails no doubt leave the host by the hole through which the 

 mother entered, and when outside must try to find a new specimen of 

 the brittle-star into which they can penetrate. Probably this parasite 

 belongs to, or is related to, one of the two other sac-shaped, shell-less 

 Gastropods known, Ctenosciihmi, Heath (in Brisinga), or Aster ophiliis, Fig. 19. Embryo of 

 Randall and Heath (in Pedicellaster). parasitic Gastropod 



rjy ,1 ■ ■ r ^ J L ^1- • /^- • J- horn Amphiura Bel- 



1 wo other specimens are mrested by the curious Cirnpedian para- ^ 



. . . gicae. X42. 



site, Ascothorax, which looks like a pea, but with a furrow from which 

 protrude two pairs of short limbs. Indeed, it very much recalls an Ostracod. This 

 parasite, like the above-mentioned Gastropod, lies wholly within the body of the 

 brittle-star, but inside a rather heavily plated cyst, opening through a pore in the 

 ventral interradius. (The Gastropod does not lie within a plated cyst.) Neither of the 

 two parasites castrates its host. 



The fact that only so very few specimens have been taken off the Falkland Islands 

 (Sts. WS 228, WS 244, and WS 840) indicates that hereabout is the northern limit of 

 the species, it being apparently very rare in this region. (About the identification of 

 these specimens I have no doubt.) 



Amphiura da Cunhae, n.sp. 



St. 1187. iS. xi. 33. Off Inaccessible Island, Tristan da Cunha, 135-134 m. 8 specimens. 



Diameter of disk of largest specimen 3 mm., arms ca. 15 mm. long, rather slender. 

 Disk covered with rather coarse scales, among which the primary plates are distinct, 

 particularly so in the younger specimens. The radial shields are short, one-third the 

 length of the disk radius ; they are separated by a single wedge of scales, in younger 

 specimens contiguous distally. The ventral interradii are covered by somewhat smaller 

 scales than those of the dorsal side of disk ; proximally these scales are more scattered. 



