BRANCH ARTHROPODA : CRUSTACEANS 151 



Note the division of the body into the head, thorax, and abdomen ; 

 find the eyes, the antenna; and the mouthparts (mandibles and maxillae 

 are usually pressed closely together). All the locomotory append- 

 ages are adapted for walking or running, not swimming. Note the 

 number of pairs of legs ; the structure of a leg ; find gills and gill- 

 covers. Some females may be found with eggs on the under side 

 of the thorax near the bases of the legs, the eggs being covered by 

 thin membranous plates. Make drawings snowing the general 

 form and character of body and details of legs, gills, etc. Compare 

 with the crayfish and Cyclops. 



The wood-lice (fig. 36) are among the few Crustacea 

 which have a wholly terrestrial life. They run about 

 quickly and feed chiefly on decaying 

 vegetable matter. They are night 

 scavengers. They have the body 

 oval and convex above, rather pur- 

 plish or grayish brown, and smooth. 

 Although they do not live in the 

 water they breathe partly at least by 

 means of gills (though they may 

 breathe partly through the skin). 

 It is therefore necessary for them to 

 live in a damp atmosphere so that the 

 facoi seci^Tnot ^1 S il1 membranes may be kept damp. 



specnot 



termined. (From sped- if no t kept moist they could not 



men.) 



serve as osmotic membranes. 

 Lobsters, Shrimps and Crabs (Decapoda). TECHNICAL 



NOTE. Teachers living near the sea-shore can get specimens of 

 live and dead, lobsters, shrimps, and crabs in the markets. Schools 

 in the interior should have a few preserved specimens for examina- 

 tion. These specimens should be compared with the crayfish ; 

 although differences in shape of body are evident, the character 

 and arrangement of body parts will be found to be very similar. 



The largest and most familiar Crustaceans, as the cray- 

 fishes, lobsters, shrimps, prawns and crabs, all belong 

 to the order Decapoda, or ten-legged Crustacea. The 

 members of this order have, including the large claws, 

 ten walking feet; they all have eyes on movable stalks, 



