SECT. X 



PHYLUM ARTHROPODA 



231 



The other sub-class is the Entomostraca. The Entomos- 

 traca, which are even more numerous than the Malacostraca, 

 are of comparatively simple organisation, and usually of small, 

 often almost microscopic, size. The number of segments is 



FIG. 123. Pagurus bernhardus. ch. chela of first right leg ; 1.4, t.j, fourth and 

 fifth legs ; t. abdominal terga ; up. uropods. (After Bell.) 



variable, and the appendages are not so highly differentiated 

 as in the Malacostraca. A carapace developed from the 

 head is often present. There is no gastric mill, and the 

 renal organs are not antennary glands, but shell-glands 

 opening at the bases of the second maxillae (Fig. 124, 



