FEATHER-STARS, RECENT AND FOSSIL. 
201 
of these bundles, at the hinder end of the larva, rests against a 
circular plate of considerable relative size. At this stage the 
larva has the form of a bent club or rod with an enlarged head. 
The ciliated bands disappear, and it gradually loses its power 
of swimming, attaching itself to some stone or other solid sub- 
stance by its base, the knob of the club being free (woodcut c). t 
This knob gradually becomes the body of the future Comatula ; 
while the series of rings between it and the base of attachment 
make up a short supporting stem. This is known as the Penta- 
crinoid stage of development, owing to the resemblance between 
it and another Crinoid ( Pentacrinus ) which remains stalked 
throughout life, while the larval Comatula is only so for a time. 
For it eventually separates itself from all but the top joint of its 
stem, and anchors itself by the cirri that are developed upon 
this top joint, which developes into the permanent centrodorsal 
piece, being rather larger than the ‘other stem-joints from the 
very first. The ring of plates resting upon it are the basals, and 
the plates above them, the orals. The enlarged head gradually 
becomes five-lobed, each lobe answering to an oral plate ; and 
after a while these plates separate like the petals of a flower 
so as to expose in the centre ( Antedon ) the opening of the 
permanent mouth. Around it are five groups of three tentacles 
each, alternating with the oral-lobes. At this early stage no 
radials are present, but only the basal-plates resting upon the 
centrodorsal piece beneath, and supporting the orals above. 
The space between these two rings gradually increases, the 
orals being carried away from the basals as the calyx widens 
out. The first radials appear in this intervening space between 
the basals and orals, alternating in position with both ; and in 
correspondence with them the rays grow out as rapidly- 
elongating processes, in which the other radials are success- 
ively developed, so that the diameter of the calyx increases 
fast. The oral plates retain their primitive relation to the 
mouth, and so get carried further and further away from the 
basals, while the first cirri begin to appear on the centro- 
dorsal ring that supports the basals. The orals gradually 
become absorbed, and soon after the head detaches itself from 
the stem and commences life as a free Comatula they dis- 
appear altogether. At the same time the basals undergo a 
very singular series of changes which result in their being no 
longer visible on the exterior of the calyx. 
Very soon after the young Comatula is detached from its 
stem, the centrodorsal begins to extend itself over the dorsal 
surface of the ring of basals so as finally to conceal it altogether. 
At the same time the shape of these plates becomes altered by 
removal of one part and the deposition of new calcareous matter 
at another part. The original ring of five pentagonal plates 
thus undergoes transformation into the ‘ rosette/ a small ten- 
