480 TENTACLES OF THE ECHINUS—MADRY. 
nearly all. Writing now from recollection, my impression is that 
a portion of one row was still pellucid. I hazard the conjecture 
that besides their locomotive function and their function of 
resisting motion, the tentacula of the Echinus have also the office 
of aiding in the nutrition of their possessor. 
Fig. 3 presents a view which explains most interestingly the 
minute anatomy of the terminal disc. It exhibits, of course, 
only a portion of the organ. The area cdex is composed of a 
formless material in which irregularly roundish masses (pro- 
bably calcareous) are embedded. They are independent one 
of another. This secures perfect freedom of movement and 
enables the disc to apply itself to any conceivable form of 
surface, smooth or rough. Moreover, projecting in pairs from 
the outer portion of this plastic foot (?) are denticles (@ a @) 
which serve, I conjecture, the double purpose of clinging and 
of comminuting food. Their plasticity gives them a clawlike 
grasp. 
It is to be observed that the bundles of muscular fibre, which 
seem in the figure to radiate from the points of the denticles, 
are not attached to these points. For, focussing upon the denti- 
cles, it is perfectly clear that the tendons of the muscular bundles 
are in a different plane from that of the denticles. They are 
hazy when the denticles are clear. They must, therefore, be at- 
tached at points interior to the denticles, these being absolutely 
superficial. 
The double circular band, yy, is quite distinct. Whether it is 
nervous or muscular I could not safely say. 
