8 4 



CRABS AND INSECTS. 



brine-shrimp (Fig. 91), live in the brine-vats of various coun- 

 tries, the amount of salt sometimes determining the form 



FIG. 91. Brine-shrimps, a, Branchi- 

 pus stagnalis. d, Artemia salina 

 whose form depends upon the salt- 

 ness of the water. 



FIG. 92. Fresh -water 

 crustacean, with bi- 

 valve shell. *?, eye. 

 (After Morse.) 



of the animal. They multiply by budding and by eggs. 



The Estheria (Fig. 92) secretes a bivalve shell, microscopic 



rings upon it indicating 

 the various moults, the 

 cast - off coat being ce- 

 mented to the new shell 

 which forms beneath. Si- 

 da and Daphnia are called 

 water-fleas from their ac- 

 tivity. The latter carries 

 its eggs upon its back. 

 The Apus (Fig. 93) is an 

 interesting form, having 

 forty-seven segments and 

 as many as sixty pairs of 

 limbs. They withstand 



remarkable extremes of 

 heat and coldj the eggs 



hatching in snow - water 



after being frozen for two weeks. The Nebalia, repre- 

 senting Order IV, Phyllocardia, has leaf-like feet, and 



