56 NEW SPECIES OF HYALINI: DAPHNIA 
of feet until it rests against the abdomen, then it is forcibly 
thrust out, expelling the material into the water. On the 
contrary, if the residue is suitable, then the labium or 
upper lip, shapen into a broad fleshy plate, with bordered 
hairs, and hinged by its upper part to the chest, is lifted, 
and a portion of food enters the mouth. The lip, like a 
trap-door, then falls down over the orifice. Beneath lie 
a pair of minute but powerful jaws, with four semi-circular 
teeth, directed towards each other. These tear the mass, 
and force it towards the mandibles. These are peculiar in 
shape, and interesting in their operation. They li parallel, 
and in front of the alimentary canal. In shape, conical, 
with the extreme point pivoted, leaving the body free to 
rotate. The sides of the cones which face each other are 
somewhat flattened, but basally are rounded, and hardened 
with chitine. On the ends of each, which face, is developed 
a hard oval plate, grooved with parallel bars, three stout 
teeth also project on the edge. A second set of teeth 
in the form of a comb, with the longest teeth set in the 
centre, the others gradually diminishing as they approach 
the sides, is set at an angle of about thirty degrees from 
the surface. By the action of the jaws, the food is forced 
towards these rasp-like plates and teeth. Then there 
comes into play a peculiar muscular mechanism. The 
cones, pivoted at their further pointed ends, and held in 
place by bands of muscles, are given a quarter of a revolu- 
tion in one direction ; then reversed in the opposite way, 
and so they rock back and forward, with the regularity 
of a pendulum. By this means the food is crushed into 
a fine pulp. As I watched the process there came to mind 
the quotation :-— 
“The mills of God grind slowly, 
But they grind exceeding small.” 
On the inner surface of the labium the cesophagus opens: 
and ascends to the large curvature of the digestive canal ; 
throughout its length, thick, transverse muscles surround it- 
By their contraction the comminuted food can be seen 
forced in little jets on its upward way to the stomach. On 
the back of the labium, a stout cord-like muscle rises in 
the median line. At its origin is a tuft of tactile papilla, 
continuing to the head it divides, a branch running to each 
