CRABS, HERMIT-CRABS, AND OTHER CRUSTACEANS. 145 



The figure 134 represents a small species which is com- 

 mon in stagnant pools in nearly all the Northern States. 



From this species the pupils may study a form in which 

 the segments of the thorax are not covered by a continuous 

 shield. 



The sowbug is a crustacean which lives out of water, 

 though always requiring damp surroundings. It may be 

 collected under logs and stones. In this creature the seven 

 segments of the thorax are easily counted. 



FIG. 135. COMMON SOWBUG. The line shows the length of the specimen from which this 



figure was made. 



The eggs of the sowbug, as well as those of other species 

 of crustaceans of the same group, are carried on the under 

 side of the thorax and between the legs, in a little brooding 

 cavity made by leaf-like parts which lap over each other 

 and hold the eggs in place. 



The eggs of these crustaceans may be found by examin- 

 ing the under side of the body, and observing a lightish- 

 colored space between the legs. With a pin or the point 

 of a knife-blade they may be scraped away without injuring 

 the animal. They are very minute, and only under the 



