STOMATOPODA. 



301 



Later stages, which are distinguished by the transformation of the 

 sixth pair of pleopoda into the lateral appendages of the caudal fin, 

 bring about the transition to the actual Erichthus stage (Fig. 142), 

 the three posterior maxillipedes gradually reappearing and the 

 hitherto missing pairs of limbs of the last three thoracic segments 

 growing out as buds. When the rudiment of the rounded prehensile 

 claw can be recognised on the last three maxillipedes, and the three 

 posterior thoracic appendages are seen as rods which soon become 

 biramose, the Erichthus stage appears to be reached. This stage 

 thus possesses all the limbs of the adult form. The transition into 

 the sexually mature form is accomplished very gradually, the 

 abdomen continually increasing in size, and the branchial filaments 

 (br) growing out on 

 the exopodites of the 

 abdominal limbs. The 

 larval forms which bring 

 about this transition to 

 the sexually mature 

 animal, when exhibiting 

 broad and compact 

 bodies and retaining the 

 appearance of the Erich- 

 thus, are known as 

 Squillerichthus, while 

 certain ontogenetic 

 forms which, even in 

 the Erichthoidina and 

 Erichthus stages, are 

 remarkable for their 

 slender bodies, pass from 

 the latter into a Squilloid 

 stage (Claus) which 

 more nearly resembles 

 the adult form. 



A second Stomato- 

 podan ontogenetic series 



consists of the Alima forms. These larvae (Fig. 144) are distin- 

 guished by their great size, the length of the body, and the broad, 

 Hat cephalo- thoracic shield, which usually does not cover the 

 posterior thoracic segments; further, by the position of the mouth, 

 which has shifted far back, and by the slight forward extension 



Fig. 143.— Squilloid larva (so-called Pseudozoaea), after 

 Claus. a', first antenna ; a", second antenna ; I, II, 

 first and second maxillipedes ; ep, epipodial appendage ; 

 ai-a 6 , the six pleopoda. 



