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 



Fio. 175. 



Larval stages of Sergestes. A, Protozoea-, B, Schizopod -stage (Acanthosoma). a', antennule ; 

 a", antenna ; mf'-mf", the three pairs of maxillipeds ; mz', maxillula ; mx", maxilla ; ol, labrum ; 

 sd, maxillary gland. (After Glaus, from Korschelt and Heider's Embryology.) 



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 



