MOLLUSCA. 205 
little substances, alive or inanimate, the current of water 
brings, flows in unless stopped by the tentacula, and they do 
not appear fastidious, to the mouth, and lodge somewhere 
on the sides of it. A lively animalcule will sometimes dis- 
engage himself by struggling, and dart about in the cavity 
till he lodges on some other part ; or, if a morsel is found 
unsuitable, it is ejected by the funnel’s being closed, and 
the branchial sac suddenly contracted vertically. Mostly, 
however, whatever part the food lodges on, it travels from 
thence horizontally with a steady slow course towards the 
front of the cavity, where it reaches a downward stream of 
similar materials, and they proceed together, receiving ac- 
cessions from both sides, and enter at last at the bottom, the 
cesophagus : this is a small flattened tube which carries them, 
flowing on in the same way, without any effort of swallow- 
ing, towards the stomach. The tube takes a sharp curve 
upwards and backwards before arriving there. 
It is extraordinary that these particles pass along in the 
mouth just behind the spiracles, when the ciliae are in full 
activity, without being at all affected by them. I have, in 
some positions, seemed to catch a glimpse of a membrane 
suspended within, too transparent to be commonly seen. 
One may imagine the water to pass to the spiracles, strain- 
ed through the meshes of such a membrane, and the food 
to be carried along it by invisible villi; but this is mere 
conjecture. The projecting fingers have the effect, whether 
intended for such a purpose or not, of detaining some pri- 
soners more bulky than the usual food of the animal, for, in 
several individuals, I met with small shrimp-like crustacea 
confined between the rows: one escaped during an obser- 
vation, another, after three days, seemed as lively as when 
first swallowed. 
