THE DECAPODA 



299 



of which two races are known, the one found in Southern Europe 

 being exclusively freshwater in habitat ; the other, found in Britain 

 and Northern Europe, inhabiting brackish or salt water. The 

 former hatches at a stage when all the limbs except the uropods 

 are present, and the first two pairs of legs have exopodites. In 



B 



FIG. 17X 



Larval stages of Sergestes. A, Protozoea-, B, Sehizopod-stage(^ca?it7ioso)na). a', antennule ; 

 o", antenna ; mf'-inf", the three pairs of maxillipecls ; MX', maxillula : mx", maxilla ; ol, labrum ; 

 ml, maxillary gland. (After Glaus, from Korschelt and Heider's /,'/'/;//'>/'<;///.) 



the northern race all the ambulatory legs are rudimentary on 

 hatching, and there are no abdominal limbs. 



None of the Astacura are known to possess a Zoea-stage. The 

 Lobster (Homarus) is hatched in the Schizopod-stage (Fig. 176), 

 with natatory exopodites on all the thoracic limbs, but without 

 any abdominal appendages. In the further course of development 



