NATURAL HISTORY. 09 
observed to move along the arms and body by 
the contraction and dilatation of the animal, 
like the peristaltic motion in animals which 
have a separate digestive cavity. No circulat- 
ing or radiating system is therefore necessary 
for conveying the nutritive portion of the food 
to the different parts of the creature, each por- 
tion performing that office for itself. The small 
granulated bodies diffused throughout the sub- 
stance of the animal are probably the glands, 
by which the assimilation of the food is effected 
—an opinion which is strengthened by the fact 
that the colour of these granular bodies ap- 
proximates to that of the food, while the 
other parts of the animal are colourless. 
No nervous or respiratory organs have been 
discovered in these creatures; indeed, I con- 
ceive the latter function, if necessary in ani- 
mals of this kind, may be amply performed by 
absorption at the surface of the animal itself, as 
this surface is vastly greater in proportion to the 
mass of the animal than are the lungs, compared 
with the body of the higher orders of animals. 
They move about from place to place by 
alternately fixing themselves by the head and 
tail; they can descend or ascend in the water at 
pleasure; they also move along the surface of 
