414 
placed in ajar of sea-water, and the embryos were examined from 
day to day. 
Segmentation appears to take place in this species in the way 
usual in the class, and involves the whole yelk. After segmenta- 
tion, the embryonic mass is at first spherical, finely granular, and 
still invested by the vitelline membrane. This membrane soon 
disappears, and within a few hours the embryo seems perfectly 
homogeneous, regularly oval, and of a delicate flesh* colour. No 
trace of cilia could be detected at this stage on the surface. Four 
or five hours later, the oval form is still more marked ; one end has 
become slightly dilated, and towards this end there is an accumula- 
tion of the granular substance. The whole embryo is now invested 
by a delicate structureless gelatinous layer, which is thinner and 
less apparent towards the narrower end of the oval. At the broader 
end it invests a dark consistent granular layer, of considerable thick* 
ness, formed of oil globules, and compound-granular masses and cells, 
which lines a central cavity, filled with a clearer granular semi-liquid, 
in which there are traces of molecular or ciliary motion. 
The transparent investment of the narrow end now protrudes 
three tubular processes, two long and narrow, turned in one direc- 
tion, and the third, shorter and thicker, turned in the opposite direc- 
tion. Between these tubes in the centre there is a raised whitish 
imperforate tubercle. Each tube is dilated at the extremity into a 
slightly opaque rounded bulb, which at length takes the form of a 
sucker, undistinguishable from the ambulacral suckers of the young 
star-fish. 
The granular fluid of the embryo still passes freely into the tubes 
through their wide common base. 
This common base now contracts and lengthens ; and this nar- 
rower portion of the clavate embryo is separated by a distinct line 
of demarcation from the broader mass, which gradually assumes a 
rounded and then a pentagonal form. The embryo during these 
changes increases rapidly in size. The peduncle, with its tubular 
appendages, now assumes its definite and final form — a wide trans- 
parent contractile tube, prolonged inferiorly into three, or sometimes 
four, wide tubular branches, terminated by suckers. The contents 
of the peduncle and tube-feet consist of a clear colourless fluid, in 
which chyle corpuscles, of the usual form, move and circulate with 
the motion peculiar to such particles in the vessels of the ecliino- 
