480 
POPULAR SCIENCE REVIEW. 
centre of which, is the lowest part of the funnel. By this con- 
trivance, then, there is a constant rush of water down the tube, 
carrying with it whatever of floating atoms it may hold in 
suspension. These are poured down upon the lower jaws ( ram i) at 
the point where they are hinged together, as represented by 
the stem of the semi-apple, a sort of valve in the tube shutting 
out whatever would be hurtful or unfit for food. They are then 
spread along and between the jaws — the apple-quarters, — which 
are vigorously opened and closed alternately, with a rapid 
rolling movement. Thus the points of the upper jaws (mallei), 
represented by the two sets of pins, working towards each 
other, bruise and pierce the infusoria, or the atoms of organic 
matter, poured along the faces, and gradually grind them down, 
while the result passes off by the lower tube (oesophagus) into 
the stomach for digestion. 
I have dwelt the longer on this matter because the same 
illustration serves to explain the process and organs of the 
reception of food, not only in this family, but in almost all the 
Botifera. The subject is full of difficulty and obscurity to 
beginners, and it was not till after years of laborious study that 
I myself succeeded in elucidating the details ; but once mastered, 
a large part of the structure and economy of these little crea- 
tures is intelligible. After the action of the ciliary “wheels/’ — 
which is sure to be the first thing that arrests the attention and 
wonder of the beholder, and which is in no species seen to more 
advantage than in those of the present family, — the movements 
of the mouth (or gizzard of the older writers) attract notice, and 
we wish to know the meaning of them; the form and character 
of the very complex organs inclosed in this curious bulb, their 
connexion with the surrounding 1 parts, and the object of their 
almost incessant vigorous wnrking'. I may find occasion, 
hereafter, to show by what steps I have arrived at the conclu- 
sion that this apparently internal organ, the so-called gizzard , 
is a real proper mouth, and its indubitable analogy with the 
parts of the mouth in Insects. In the forms we are now con- 
sidering it is so much disguised and modified that I could 
scarcely hope to make myself understood ; but we shall come 
to species by-and-by in which all the parts described above are 
readily identified, but so altered in shape, and especially in 
position, that we shall see at once that they form two pahs of 
real jaws, very closely resembling those of a biting insect. For 
the present I content myself with hoping that by the aid of 
apple, pins, and wax, the reader will have no difficulty in form- 
ing a tolerably vivid idea of the organs as they appear in this 
family, and a correct notion of what are their functions, and 
how performed. 
