FOOD AND FEEDING 



paired and one central single eye. It has two pairs of threadlike an- 

 tennae. Under the shell there are 60 pairs of gilled 

 legs, of which the first pairs are developed into anten- 

 nse-like feelers. It swims on the back, and steadily 

 moves through the water by rapid undulating strokes 

 of the legs. The periodic appearance of this Crustacean 

 may be due to the fact that the eggs must be subjected 

 to a period of incubation in the dry earth. The food 

 consists of water animalculse and decaying vegetation. 

 It is the larv£e and young of these Branchiopods 

 which constitue the food of the mature goldfish, 

 the adult being of too large size to be readily 

 taken. It is principally the Crustaceans of the follow- ^ ' Gte^h/^'lnhrgld"""''^' 

 ing sub-order Cladocera which constitute their live food. 



Sub-order Cladocera. Compressed body small, indistinctly seg- 

 mented, enclosed in a bivalve carapace, four or six swimming feet, and the 

 posterior antennas developed as longer swimming feet. The most general 

 forms are Daphnia, Polyphemus arid Leptodora. Daphnella, Sida and 

 Ciriodaphnia also belong to this sub-order. 



Daphnia. Fig. 66. Four or five species of Daphnia, known to the 

 goldfish breeder by their light green, 'dark green, red and reddish colors, 

 abound at different seasons in almost every still or stagnant water. Their 

 size is from .75 to 1.5 millimeters. The segmentation 

 of the body is imperfect, the Crustacean being covered by 

 a folded carapace. The head is distinct and the abdomen 

 is turned downward and is in constant movement. The 

 long antennae are moved at longer or shorter intervals, 

 making the progress a series of rapid starts and stops. 

 Between the abdomen and the carapace of the female 

 is a large brood pouch in which the eggs are stored 

 and hatched and the larvae only make their escape 

 when they have reached the free-swimming stage. The 

 paired eyes have fused into a single organ. There are 

 five pairs of swimming legs on the thorax. The re- 

 production of the Daphnia is most curious. During the summer the 

 female develops spores, which, without fructification by the male, develop 

 in the brood pouch to perfect Daphnia in four days, and which, when they 

 have become liberated, in a few days reproduce in the same manner. In 

 the fall of the year the much smaller males appear and the sexual repro- 

 duction takes place. Winter eggs are produced, the thick shells of which 

 protect them through the cold season. The food of the Daphnia is de- 



FIG. 66. Daphnia pulex. 

 Greatly enlarged. 



119 



