198 NATURE’S CRAFTSMEN 
it is a descendant of the forms outside which pos¬ 
sess perfect sight. While most crustaceans are 
solitary, a few like the shrimp much used for 
food, and the barnacles, are to be found banded 
together in vast shoals. There are more than 
10,000 species of Crustaceans known, and their 
value can scarcely be computed. The myriads of 
smaller forms constitute the chief fare of the 
fishes, and are thus indirectly valuable to man¬ 
kind ; while as natural scavengers all of the larger 
Crustacea are of vast economic importance. 
“ The crawfish in common with other.'; of his 
kind moults, or sheds his crust, whenever it be¬ 
comes too small for his body. While the baby 
crawfish is growing up, it moults frequently; later 
on in life the moult occurs but once a year. When 
about to don a new suit the animal retires to a 
secluded spot. It is a sorry bother, and bound 
to be more or less ludicrous. No doubt the little 
creature is quite wise in avoiding the eyes of 
others. After a few days of hunching with arms 
akimbo in the general discomfort of an extremely 
tight-fitting suit, the seam between the carapace 
and abdomen finally gives way, and the crawfish 
after many wriggles and contortions finally man¬ 
ages to slip out of the old shell. His body is now 
soft and unprotected, and he is, moreover, so 
tired and weak from his exertions that he is an 
easy prey if any enemy chances upon his retreat. 
