VIII 



ARTHROPODA 



199 



at' 



converted into the mandible. The first two pairs of thoracic legs 

 are each now distinctly divided into two branches, but both exopodite 

 and endopodite are as yet un- 

 divided. The bifurcation of the 

 caudal end has now deepened, so 

 that the anus is guarded on each 

 side by a rod-like appendage one 

 half of the caudal fork. In the 

 base of the second maxilla may be 

 seen the sac-like rudiment of the 

 shell-gland the adult excretory 

 organ, whilst the antennary sac 

 has disappeared. The thoracico- 

 abdominal rudiment is now dis- 

 tinctly divided into segments. 



At successive moults additional 

 joints are added to the first 

 antenna, the branches of the 

 thoracic legs become jointed, 

 and the posterior thoracic legs 



B 



csp 



FIG. 146. Two types of Nauplius larva. 



A, tlie Nauplius larva of Bnun'hii>iix .-.Vi/i/im//* (after Glaus) combined from two liuun's. li, the 

 Nauplius larva of Lejwts (after Groom). Letters as in pivri'ding figure. In addition, ''.*/'. faudal spine ; 

 il.t.l', dorso-lateral spine; //./, frontal filament ; fil, glandular mass in the base of the dorsi.-l.ilri.il 

 spine; f/H 1 , gnathobase of antenna ; gii", gnathobase of mandible; >/, segments Jn tin: tlioracico- 

 abdominal rudiment of the Nauplius of Braiirfiiptis ; r.N/', the pre-anal spine. 



