406 
ORIGINAL ARTICLES. 
three transparent tabular processes, two turned in one direction, 
narrow, four or five times longer than their width—the other turning 
in an opposite direction, shorter and thicker. 
The investing membrane of the tubes is transparent, delicate, 
transversely wrinkled, and highly contractile. Each tube is dilated 
at the free extremity into a slightly opaque, rounded tubercle, which 
at length takes the form of a sucker, undistinguishable from the am¬ 
bulacra! suckers of the young starfish. The dark granular fluid of 
the embryo still passes freely into the tubular processes, through 
their wide, common base. 
This common base now contracts somewhat, and lengthens, and 
this narrower portion of the clavate embryo is separated by a dis¬ 
tinct line of demarcation from the broader mass, which gradually 
assumes a still more rounded and definite form. The whole embryo, 
during all these changes, increases rapidly in size, partly by the im¬ 
bibition of water through its walls, and partly by the assimilation of 
organic matter through its general surface. 
The dark upper part is now rounded or widely pentagonal ; a 
thin, transparent, structureless layer, with scattered oil-cells, covers 
the whole surface. A dark, granular band lines the transparent wall, 
and the central space, lighter in colour and more transparent, is 
filled with a mucilaginous liquid, turbid with oil-globules, granules, 
and compound granular masses. 
The lower (anterior) end consists of a wide, transparent con¬ 
tractile tube, prolonged anteriorly into three tubular branches. In 
the centre, between the branches, there is a dark oval granular 
patch, but certainly no opening. 
The peduncle and tubular appendages now assume their definite 
and final form. 
A slight constriction cuts off the peduncle, into which the pro¬ 
cesses unite, from the main embryonic mass. The contents of the 
peduncle and tubes become more and more transparent, till they 
consist merely of a clear, colourless fluid, in which corpuscles, of the 
usual form, move and circulate, with the motion peculiar to such 
particles in the vessels of the Echinoderms, and which would seem 
to be produced by cilia, though the cilia themselves have not as yet 
been detected, 
The embryo adheres to a foreign body by the suckers at the end 
of the tubes, and moves along in a peculiar uncouth manner, by the 
contraction and expansion of the three feet. At this stage the 
peduncle is attached to the lower surface of the pentagonal rudi¬ 
mentary star-fish, slightly excentrically and midway between two of 
the rays. 
25. The starfish, though now only about once and a-half the 
size of the peduncle, has asserted distinctly its Echinoderm cha¬ 
racter. 
The angles of the pentagon project still further, forming the 
rudimentary rays. The transparent external layer becomes thicker, 
