NURSING ECHINODERMS. 
59 
to the northern A. Andromeda , which was dredged in January 
from a depth of thirty fathoms off Cape Maclear on the south- 
east coast of Kerguelen’s Land. It is rather a large starfish, 
attaining a diameter of four or five inches from tip to tip of the 
arms, and the whole dorsal surface is covered with a pavement- 
like mosaic of irregularly hexagonal plates. These plates, how- 
ever, are not directly imbedded in the skin, but supported upon 
rather slender shafts, so that the whole space covered in by them 
forms a great series of columned arcades. From the ovarial 
openings the eggs, when mature, escape into these arcades, and 
they may be seen in great numbers in the spaces between the 
shafts of the paxilli, when the arms are bent so as to separate 
the hexagonal plates of the surface. The discharge of eggs into 
the brood-chamber appears to be continued for some considerable 
time, and thus eggs and young in different stages of develop- 
ment are to be found together in the spaces. In the young no 
traces of the formation of a locomotive pseudembryo could be 
detected, but it is possible that, as in P ter aster militarise in 
which the process of development is very similar, some pro- 
visional organs may exist at an early period. 
The young animals remain in the brood-chamber until at 
least six ambulacral suckers are formed on each arm, but when 
they have attained this degree of maturity they make their way 
out into the world by pushing through between the hexagonal 
surface-plates of the paxilli. The first part of the young animal 
that makes its appearance is always the oral surface, in general 
the very centre of the body with the mouth ; the arms are gra- 
dually disengaged afterwards. The young generally make their 
escape from the nursery between the plates near the re-entering 
angles between the arms ; there they remain for some time 
clustered, adhering to the surface of their parent in some mys- 
terious manner by the centre of the dorsal surface. Sir Wyville 
Thomson was unable to ascertain by what means this adhesion 
is effected, but he says that the attachment is very slight, and 
that the young animals are removed by the least touch. They 
remain adherent, however, until they have acquired about 
twenty tentacular feet in each arm, when they cast themselves 
upon the world to shift for themselves. It is curious that in the 
young the madreporiform tubercle exists near the margin of the 
disc between two of the arms, whilst in the adult it appears to 
have sunk down beneath the stalked paxilli, and is completely 
concealed. 
Another nursing starfish belongs to the genus Hymen aster, 
established by Professor Thomson some years ago ( t6 Depths of 
the Sea,” p. 120) for a small starfish dredged off the north of 
Scotland in 500 fathoms of water. The dredging operations of 
the Challenger have shown that this genus is very widely dis- 
