LARVAE OF SERGESTES 



17 



uropod. The apex is truncate, with a very small spine at each angle and a pair of setae 

 and spines between. 



Eye with very long stalk, the whole about one-third the length of the body. Antennal 

 scale very long and slender, with long apical spine ; flagellum nearly twice length of body, 

 without curved setae. 



Fig. 9. S. corniitus. a, Mastigopus i ; b, telson. 



Mandibular palp very small, unsegmented. Maxillipede 3 reaching far beyond anten- 

 nules. Hansen has noted the great length of this appendage in young Mastigopus as 

 compared with the adult, a feature which would, if its later development were not known, 

 place it in Hansen's group H. Legs with small vestiges of exopods. Pleopods long, with 

 small rudiment of endopod on pleopod 5 only. Uropod with bare part slightly longer 

 than setose part (1-09 : i). 



Stage 2 (Fig. 10) differs very little from stage i. The legs have no vestiges of exopods, 

 and the pleural spines are reduced. In this specimen the dorsal spines of abdominal 

 somites 1-3 were lost. 



Two pairs of "luminous organs" (organs of Pesta) in the thorax were noted in 

 specimens of 8 mm. upwards. At a size of 9 mm. the mandibular palp is of full size, but 

 with relatively few setae. The form of the uropods is also changed to that of the adult. 

 The antennule of the male takes the adult form in the last Mastigopus of 12 mm. 



