Ostracods 



187 



progeny of a single female might reach the astotmding 

 number of 13,000,000,000 in sixty days. 



The Ostracods are minute crustaceans, averaging 

 perhaps a millimeter in length, having the head, body 

 and appendages all inclosed in a bivalve shell. The shell 

 is heavier and less transparent than that of the water 

 fleas . It is often sculptured, or marked in broad patterns 



Fig. 93. One of our largest water-fleas, Eurycerus lamellatus, 

 twenty times natural size. Note the eggs in the brood chamber 

 on the back. Note also the short beak and the broad post- 

 abdomen (shaped somewhat like a butcher's cleaver) by which 

 this water-flea is readily recognized. 



with darker and lighter colors. The inclosed appenda- 

 ges are few and short, hardly more than their tips show- 

 ing when in active locomotion. There are never more 

 than two pairs of thoracic legs. The identification of 

 ostracods is difficult, since, excepting in the case of 

 strongly marked forms, a dissection of the animal from 

 its shell is first required, 



