ENTOMOSTRACA. 



33 



its turn to be eaten. These creatures are omnivorous. Infusoria, rotifers, eggs, and 

 embryos of small animals, diatoms and other algas, vegetable debris of all kinds are 

 acceptable. The sole 

 condition is that the 

 food shall not be too 

 large to enter into the 

 cavity of the shell. The 

 animals are not without 

 taste, as may be seen by 

 feeding them with car- 

 mine. At first your 

 Daphnid seems to re- 

 joice in the abundant 

 food-supply, flaps its legs 

 vigorously, and accumu- 

 lates a mighty supply 

 between them ; but as 

 soon as it has tasted 

 the unaccustomed viand 

 its mood changes. It 

 works its oesophagus 

 backward, reverses the 

 action of its jaws, spits 

 out the food, and with 

 the terminal claws on 

 the tail carefully scrapes 

 out and kicks from the 

 shell cavity the carmine, 

 and even cleans out its 

 mouth with the same implements; then sulks and refuses to draw in a current of 

 water laden with such particles. 



The Cladocera have an extraordinarily great power of reproduction. All through 

 the summer they produce brood after brood of " summer-eggs," which are simply buds 

 detached while still in the condition of a single cell, and resembling eggs in all 

 external particulars. They develop, however, without fertilization, while the true 

 egg will not do so. These buds or summer-eggs are carried in a brood chamber 



oo OO 



formed by the dorsal part of the valves. This varies greatly in size and shape in 

 different genera. In the Lynceidre it is small and imperfectly closed, and rarely con- 

 tains more than two large eggs. In the Daphnias there are often a dozen or more 

 eggs, sometimes as many as forty or fifty, which are enclosed in a much more 

 perfectly closed brood chamber, and nourished by fluids excreted by the mother into 

 this cavity. The young develop directly, without metamorphosis, and hatch in the 

 form of the parent. They remain for a day or two in the cavity after hatching, while 

 the shell hardens and the muscles gain strength. They are at this time quite active, 

 and cause much trouble to the parent in keeping the numerous brood in the cavity. 

 Some lively young one must always be kicked back being too hasty in his attempts 

 to see the world for himself. These broods of summer eggs are produced in rapid 

 succession, and as the young begin to reproduce when only a few days old, the rate of 

 multiplication is very great. 

 VOL. II. 3 



FIG. 41. Acanthocercus, enlarged. 



