DAVELOPMENT OF THE SEA-URCHIN. 203 
tile cilia. When the larva is twenty-three days old the ru- 
diments of the five tentacles of the sea-urchin appear. By 
this time the pluteus-form is acquired, and also at this pe- 
riod the sea-urchin growing upon the deciduous pluteus 
‘ scaffolding has congealed the shape of the digestive cavity 
of the larva, and the spines are so large as to conceal the 
tentacles. The body of the pluteus is gradually absorbed 
by the growing sea-urchin ; the spines and suckers of the 
latter increasing in size and number with age, until by the 
time the larval body has disappeared the young Echinus is 
more like the adult than the star-fish at the same period in 
sci RH 7 a mone ti te seem 
life. Grube has found that Anochanus sinensis, supposed 
to have come from the Chinese or East Indian seas, has 
no metamorphosis ; while Hemiaster cavernosus of Chili 
was found by Philippi to carry its young in marsupia and to 
develop directly. 
Several species of sea-urchins in the cooler portions of 
the South Atlantic, especially at the Falkland Islands and 
Kerguelen Island, also develop directly in marsupia or brood- 
hollows, without passing through a metamorphosis. In Hemi- 
