AMPHIURIDAE 271 



distinctly broader than long. Arm spines five on the proximal joints, short, conical. 

 Only one very small tentacle scale. Colour in alcohol whitish. 



The specimens from St. MS 68 are stated to have been taken "from the roots of a 

 giant sponge". 



This species is viviparous. The development is intra-ovarial, as may be seen with cer- 

 tainty in adult specimens, where the bursa may be distinguished as an empty sac cover- 

 ing the large ovary which is filled with eggs and embryos. There is only one interradially 

 placed gonad to each bursa ; some ten eggs may develop at a time in the ovary. I have 

 been unable to trace any male genital products in the gonads, these being purely female 

 in all the specimens, even in young specimens of 2-5-3 mm. in diameter of disk. It thus 

 appears that this species is parthenogenetic, for it is most improbable that there would 

 not be a single male in the whole collection, if the species had separate sexes. But the 

 material is too small to allow me to state definitely that such an extraordinary condition 

 as parthenogenesis occurs normally in this species. 



In one of the specimens from St. 27 the parasitic Cirripedian Ascothorax was found. 



Amphiura tnicroplax is very easily distinguished from the other Antarctic and sub- 

 Antarctic Amphiuras with one tentacle scale: A. magellanica, algida, and angularis 

 protecta. The very characteristic small tentacle scale forms a conspicuous difference 

 from these species which all have a large, elongate tentacle scale. Among other 

 Amphiuras it may perhaps find its nearest relative in A. adjecta, Mortensen (Echi- 

 noderms of South Africa, p. 355, fig. 62); possibly it is also related to A. Mullen, 

 Marktanner, from off St Paul (Marktanner-Turneretscher, Beschreibung neuer Ophiii- 

 riden und Bemerkungen zu bekannten. Ann. k. k. Naturhist. Hofmuseums, 11, 1887, p. 300, 

 Taf. xiii, figs. 25-6), but the figures of that species are altogether too unsatisfactory for 

 a detailed comparison with other species. 



Amphiura microplax, var. disjuncta, n.var. 



St. 175. 2. iii. 27. Bransfield Strait, South Shetlands, 200 m. i specimen. 



St. 363. 26. ii. 30. Off Zavodovski Island, South Sandwich Islands, 329-278 m. Several speci- 

 mens. 



St. 366. 6. iii. 30. 4 cables S of Cook Island, South Sandwich Islands, 155-322 m. i specimen. 



These specimens bear so much general resemblance to A. microplax that one might 

 be tempted to regard them as identical. They differ, however, from typical microplax in 

 having separate sexes and, probably, in not being viviparous. In the adult male speci- 

 mens the gonads are remarkably strongly developed and of a peculiar composite shape, 

 recalling an ovary with a number of large eggs. I do not remember having ever seen an 

 Ophiurid with such "composite" testes. 



The eggs are rather large and yolky, not ripening all at a time, so that they must be 

 shed from time to time as they become ripe. 



Referring to the figures it will suffice to point out the points of difference from the 

 typical tnicroplax. The outer mouth papilla is smaller, more scale-like. The dorsal arm 

 plates are usually not contiguous— but this is not a constant character ; one may even 



