THE OSTRACODA 797 



The method of propagation has been much used as a generic 

 character, but much more must be known of its constancy before 

 it can be finally accepted as at all reliable. The form of the penis 

 and of the vaginal plate, however, may both be accepted as constant 

 characters. 



The eggs are~provided with small limy shells, and commonly 

 develop in from 5 to 14 days. They are laid in characteristic 

 ways. For example, the eggs of Candona Candida are whitish, 

 and are laid singly, without being fastened together; those of 

 Cypris incongruens are orange red, while those of Cypridopsis 

 vidua are dark green. Both are laid in packets on the leaves and 

 stems of water plants, especially the under sides of Lemna leaves. 

 The eggs of Notodromas monacha are first white and later yellowish. 

 They are oval-elongate, and are laid in rows, pole to pole, on 

 the roots of Lemna. The eggs of Herpetocypris reptans are spher- 

 ical and of a yellowish color, which deepens later indeed, when 

 freshly laid, they may be almost white. 



Bottom forms, such as Candona and Herpetocypris, laboriously 

 contrive by creeping and crawling to reach Lemna and other sur- 

 face plants. They first reach the roots, and later the upper sur- 

 faces, where they appear to scrape a place with their antennae, and 

 then deposit and fasten their eggs with fine threads. All this must 

 be quite an acrobatic feat for them, as they must balance them- 

 selves meantime. After finishing, they permit themselves to fall 

 to the bottom. It is here worthy of remark that these biological 

 distinctions such as habitat, means of locomotion, food, means of 

 propagation, and egg laying, all have their value in specific 

 distinctions. 



Their eggs also have remarkable vitality. An instance is on 

 record of samples of dried mud being sent to England from Jeru- 

 salem and entomostraca being raised therefrom (Cypris and Daph- 

 nia) after a lapse of from 24 to 30 years. G. 0. Sars, of Norway, 

 has reported raising them from dried mud sent him from Australia 

 and China. In fact, he has described many new species from 

 material sent to him in this way. 



The eggs hatch into nauplii, which resemble the adult, although 

 varying much in the shape of the shell and internal structure. 



