DEVELOPMENTAL PHASES 359 



The carapace retains the lateral denticle and is unaltered except for the frontal plate, which is no 

 longer as concave as formerly. The eyes are the same. 



The flagella of the first antenna are setose and segmented. 



The second antenna has a segmented non-setose flagellum, and a scale which is setose terminally 

 and along the anterior third of its inner border. 



The cormopods are the same as in the previous stage, except that the fifth is now jointed, but still 

 non-setose. 



Sixth farcilia. Twenty-one specimens examined (Fig. \od, e). Length range 4-8-5-3 mm.; average 



length 5-1 mm. 



The terminal spines on the telson are reduced to one in number. Three abnormal specimens with 

 two terminal spines occurred. 



The frontal plate is a trifle narrower than in the previous stage, but the carapace is otherwise 

 unaltered. The tooth on the lateral margin remains. In N. simplex, it has disappeared at this stage. 



The basal segment of the first antennal peduncle shows the rudiments of the adult reflexed lappet on its 

 upper, distal margin. The spine on its outer margin reaches just beyond the middle of the third segment. 



The flagellum of the second antenna has a base with three segments and it reaches beyond the 

 scale for about half its own length. The scale bears setae all along its inner margin and a spine at 

 its base on the outside. 



The endopodite of the sixth cormopod is now jointed but that of the seventh is still unjointed. The 

 luminous organ is present at the base of the seventh cormopod. 



Juveniles (Fig. 10/). Once the outer, long, lateral spines on the telson are lost, the animal is classed 

 as juvenile. It appears to undergo about nine or ten moults before assuming a fully adult form. In the 

 course of this development the cormopods become jointed and geniculate, the frontal plate diminishes 

 and becomes adult in appearance, and the lateral denticle on the carapace disappears. There appears 

 to be considerable individual variation in the development of these characteristics. There is no 

 evidence of dominance in the juvenile series. 



Euphausia lucens Hansen 



Egg. 0-38-0-40 mm. in formalin (Fig. 11a). 



Five eggs were found and measured. They appeared to be on the verge of hatching, for all contained 

 well-developed nauplii. The nauplius completely fills the egg-case at this stage. 



Nauplius. No free nauplii were found. Those within the egg had three pairs of appendages— 

 uniramous first antennae, biramous second antennae and biramous mandibular palps. The first 

 antenna carries a single terminal spine. Each ramus of the remaining appendages is armed with three 

 spines (Fig. 1 1 a). 



Pseudometanauplius. This stage was not represented in the material. 



Metanauplius. Only one specimen of this stage was found (Fig. 1 1 b, c). 



The length of the carapace is about 0-4 mm. There is a large, elaborately serrated rostral hood. 



The first antenna is uniramous and carries three spines. 



The second antenna is biramous, the rami being armed with four and five spines respectively. The 

 exopod is segmented distally. 



The mandibular palp is reduced to a small papilla. 



The unarmed limbs of the metanauplius are partially covered by folds in the carapace. 



The telson is differentiated and carries eight spines. 



First calyptopis. Five specimens examined (Fig. iza-c). Length range 0-98-1-1 mm.; average 

 length 0-99 mm. 



