18G THE VOYAGE OF H.M.S. CHALLENGER. 



Colour in alcohol, a bleached yellowish ashy grey, sometimes with a slightly orange or 

 brownish shaile. 



Variation. — There is considerable variation in the proportions of the length of the 

 ray and the diameter of the disk, and also much difference in the breadth of the rays 

 near the base. The following dimensions may be compared with those of the figured 

 example given above : — 



R= GO mm. ; r= 1G mm. Breadth at fourth or fifth plate, 16 mm. Marion Island. 



E= 38 mm. ; r = 11 mm. Breadth at fourth or fifth plate, 11 mm. Marion Island. 



R=3Grnm. ; r=10"25 mm. Breadth at fourth or fifth plate, 8"5 mm. Station 

 149. Rays cylindrical. 



R=33 mm. ; r=ll mm. Royal Sound, Kerguelen. Disk large. 



R= 13'S mm. ; r= 5 mm. Marion Island, 50 fathoms. Rays very cylindrical. 



As a rule the larger examples are longer in the ray. 



Young Phase. — The manner in which the young are carried by the parent in this 

 species alter hatching, has already been described by Sir "Wyville Thomson 1 in a paper 

 presented to the Linnean Society. The following 2 is the account given by him : — 



" The dorsal surface of the body is covered with a tessellated pavement composed of 

 capitate paxilli. The heads of the paxilli in close apposition combine to form a mosaic 

 with rudely hexagonal facets ; and as they are raised upon somewhat slender shafts whose 

 bases, like the piuths of columns, rest upon the soft perisome, arcade-like spaces are left 

 between the skin and the upper calcareous pavement. The eggs pass into these spaces 

 from the ovarial openings : on bending the perisome and separating the facets, they may 

 be seen in numbers among the shafts of the paxilli. There is a continual discharge of 

 ova into the passages, so that eggs and young in different stages of development occupy 

 the spaces at once. The young do not escape until at least six ambulacral suckers are 

 formed on each arm ; they may then be seen pushing their way out by forcing the paxilli 

 to the side, and squeezing through the chink between them. While it is extricating itself, 

 the oral surface of the young is always above ; and the centre of the star with the mouth 

 is usually the part which first protrudes; then the arms disengage themselves one after 

 another, many of the brood remaining for a time with one or two arms free aud the 

 others still under the paxilli. When the young have become disengaged, they remain for 

 a considerable time attached to the parent by the centre of the dorsal surface. I could 

 never satisfy myself by what means this is effected ; the attachment is very slight, and 

 they are removed by the least touch. In this attached stage, until they entirely free 

 themselves, which they do when the number of tentacular feet on each arm has reached 

 about twenty, they cluster in the re-entering angles between the arms of the mother, 



1 Juurn. Linn. Sor. Lond. (Zool.), 1S76, vol. xiii. pp. 55-79. | 



s Loc. n't., pp. 71-73. Also Voyage of the Challenger, The Atlantic, London, 1877, vol. ii.'pp. 234-237, 

 where the priority of Smith's name is acknowledge! 



