NURSING ECHINODERMS. 
53 
In the order of Sea Slugs, or Holothuroidea, Sir C. Wyville 
Thomson notices two species in which the development appears 
to be direct ; but the arrangements for the shelter of the young 
are very different in them. One of them, which is identified 
with the Cladodactyla crocect of Lesson, has a curious nursery 
for its offspring, and not an incubatory pouch. It is a small 
and elegant species, attaining a length of about 4 inches, and a 
diameter of 14- inch ; its colour is a bright saffron yellow, and 
it was found abundantly adhering to the fronds of the gigantic 
sea-weeds ( Macrocystis ) floating in water from five to ten 
fathoms deep in Stanley Harbour, East Falkland Island. The 
oral tentacles, ten in number, are long and delicately branched ; 
and the skin is thin and semitransparent, allowing the muscular 
bands and other internal parts to be plainly seen. Five ambu- 
lacral rows of numerous and well-developed tentacular feet 
traverse the body from end to end, but not at equal distances 
apart ; three of them are approximated on one surface of the 
animal and two on the other, the space between the two groups 
on each side being considerably wider than that between any 
two ambulacra of the same group. The tentacular feet in the 
three approximated rows are larger than the others, and con- 
stitute, at all events in the female, the regular means of 
locomotion ; in this sex the two other (dorsal) rows subserve a 
totally different purpose, forming, as it were, the fences of the 
nursery in which the animal carries about its young. These 
tentacles are short, and although they are provided with sucking 
discs, the calcareous framework of the latter is in a rudimentary 
condition. 
It is along these two dorsal rows of tentacles, and indeed 
adhering to them, that the young animals are carried about by 
their mothers until they have arrived at a condition to shift 
for themselves, which must be comparatively late in life. 
Sir C. Wyville Thomson observed them still occupying this 
position of dependence when they were nearly half as long as 
their parents, and he describes the appearance of the mothers 
“ with older families ” as peculiarly grotesque — “ their bodies 
entirely hidden by the couple of rows, of a dozen or so each, of 
yellow vesicles, like ripe yellow plums, ranged along their 
backs, each surmounted by its expanded crown of oral tentacles.” 
The young animals are nearly perfect miniatures of their 
parents, except that, as might be expected, the tentacles of the 
two dorsal rows are quite rudimentary, or barely indicated ; 
the tentacular feet of the other three ambulacra, on the 
contrary, are very early developed, and it is by their means 
that the adhesion to the dorsal tentacles of the mother is 
effected. The placing of the young animals was not observed, 
but it seems probable that “ the eggs are impregnated either in 
