Decapoda 191 



what larger size, that live sprawling in the mud of the 

 bottom in trashy pools. Their long legs and hairy 

 bodies are thickly covered with silt. Two pairs of 

 thoracic legs are adapted for grasping and five pairs for 

 walking, and the appendages of the middle abdominal 

 segments are modified to serve for respiration. Asellus 

 feeds on water-cress and on other soft plants, living and 

 dead, are found in the bottom ooze. It reproduces 

 rapidly, and, in spite of cannibal habits when young, 



FIG. 98. Three common Amphipods. 



A, Gammarus fasciatus; B, Eucrangonyx graalis; C, Hyalella knickerbockeri. 

 (Photo, by G. E. Embody). 



often becomes exceedingly abundant. An adult female 

 of Asellus communis produces about sixty eggs at a 

 time and carries them in a broodpouch underneath her 

 broad thorax during their incubation. There is a new 

 brood about every five or six weeks during the early 

 summer season. 



Both this order and the preceding have blind 

 representatives that live in unlighted cave waters, and 

 pale half -colored species that live in wells. 



The crawfishes are the commonest inland representa- 

 tives of the order Decapoda. These have the thoracic 



