224 H. GRAHAM CANNON 



is always followed iiimiediately by a movement of the mandihlefi, 

 but the latter rotate many times without any movement of the 

 maxillae, so that ])r()bably the maxillae ])ush forwards a large 

 bolus on to the mandibles and these gradually jjass it into the 

 oesaphagus. 



Hardy and AlacDougall (8), referring to Daphnia, which is 

 no doubt essentially similar in its feeding to 8 i m o c e p h a 1 u s 

 vetulus, state that food particles are carried over the 

 mouth by a current of water and ' many of them adhere to the 

 sticky surfaces of the mouth appendages ', and that these 

 adherent particles are formed into a bolus by the movements 

 of th(^ appendages. To observe the method of feeding 

 these workers fed the Daphnids on milk, yolk of egg, and 

 carmine. When the anijuals are fed on anv of these substances 

 they always become dirty, the particles adhering all over their 

 bodies. With the former two substances they become greasy 

 and break through and adhere to the surface of the water. 

 It is thought that this is merely due to the presence of an 

 abnormally large quantity of food. In the normal animal, 

 feeding on its normal food, no particles are to be seen adherent 

 to the appendages. If the animal is at all moribund it soon 

 becomes covered M^th adherent particles. 



If the animal be fed on milk — a drop of milk is carefully 

 placed at the bottom of a watch-glass containing the water in 

 wliicli the water-fleas are swinuning — the regular movement 

 of the appendages is often stopped while the setae of the first 

 trunk-limb are combed over the lateral surface of the labrum 

 to remove any jnilk adhering to it. Also by this method of 

 feeding a large amount of fatty drops collect in the food groove 

 posterior to the maxillae. These are in all probability drawn 

 there by the backw'ash previously mentioned that must pass out 

 along this groove. When this accumulation of food becomes 

 too great the labrum is raised by its levator nmscle — which 

 runs from the base of the labrum to the covering of the brain — 

 the trunk is liexed forwards, and, with the caudal furca, the 

 accumulation is lifted out of the food groove and, by the 

 extension of the body, removed to the exterior. 



