84 CRABS AND INSECTS. 
brine-shrimp (Fig. 91), live in the brine-vats of various coun- 
tries, the amount of salt sometimes determining the form 
Fic. 91.—Brine-shrimps. «, Brancht- FIG. 92.—Fresh - water 
pus stagnalis, 6, Artemia salina crustacean, with bi- 
whose form depends upon the salt- valve shell. e, eye. 
ness of the water. 
of the animal. They multiply by budding and by eggs. 
The Zstheria (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. S#- 
da and Daphnia are called 
water-fleas from their ac- 
tivity. The latter carries 
its eggs upon its back. 
The Agus (Fig. 93) is an 
interesting form, having 
forty-seven segments and 
as many as sixty pairs of 
limbs. They withstand 
remarkable extremes of 
Fic. 93.—Apus. heat and cold, the eggs 
hatching in snow- water 
after being frozen for two weeks. The MVebalia, repre- 
senting Order IV, Pfyllocardia, has leaf-like feet, and 
