a7 
exuded from the body of the animal ; and, further, by the 
same exudation the animal keeps the particles of fine sand in 
which it lies imbedded from getting down amongst the spines 
by this substance forming a thin covering of the mucous matter 
incorporated with sand, which envelopes the body of the 
animal, and when a portion of the sand by accident gets 
down amongst the spines it is thrown out by a fresh dis- 
charge of the glutinous matter. 
That the animal possesses a supply of this substance ade- 
quate to any exigency is seen by putting the Amphidotus in 
fresh water for a short time, when it wili be found surrounded 
by a mass of slime. 
The digestive organs appear to be somewhat intricate. 
There is a peculiar process situated within the test on the 
left side of the oral opening which serves as a point of attach- 
ment for the gullet as it bends round to the left side of the 
body. 
The intestines, for there is no stomach proper, is extremely 
thin and delicate, and is ruptured by the slightest attempt to 
remove it. It is of considerable calibre, and packed with 
sand ; from the above attachment it proceeds onwards, making 
one and a half convolutions, abutting against the internal 
projection of the anterior groove; here it turns upon itself 
and makes two thirds of a convolution, reaching the left side, 
whence it turns inwards and a little backwards. At this 
point it contracts considerably (and here it contains no sand, 
but a small quantity of black pasty matter), risimg in an 
arching form to the roof of the test behind the madreporiform 
tubercle, and thence passing down to the anus. 
From the fact of no sand being found in the small gut near 
the anus, and little black pellets being the only matter seen 
to be ejected, it appears most probable that the sand does not 
pass through the animal, but is disgorged, although this I 
have neyer seen. 
