DEVELOPMENT OF EUPHAUSIA SUPERB A 99 



Antenna. The scale is more heavily furnished with setae on its inner margin than 

 in the previous stage ; the flagellum is multi-articulate and much longer than the scale 

 (Fig. 25 d). The spine on the basal segment is furnished with little bristles on its inner 

 margin. The second basal segment is indistinctly articulated with the first and appears 

 like an additional peduncular segment of the inner ramus. 



Mandible. The lacinia mobilis has disappeared on the specimen figured, and in all 

 the other larvae examined belonging to this stage no lacinia mobilis was seen. The palp 

 (Fig. 25 e) is more elongate than in the previous stage and the number of spines on the 

 distal segment is increased: the variations in spine number are dealt with on p. 67. 



First maxilla. The palp is slightly shorter and broader than in the previous stage, 

 but the masticatory lobes are similar. The larval exopod has disappeared and the 

 pseudexopod extends to the joint of the palp bearing on its margin two or three little 

 bristles (Fig. 25/). 



Second maxilla. This appendage (Fig. 25 g) consists now of three portions: distally 

 the palp, which is broader in proportion to its length than in the previous stage ; a middle 

 portion with two lobes internally and the digitate process of the exopod externally; and 

 proximally a basal portion bearing two lobes internally. 



First thoracic limb. The exopod of Th. I (Fig. 26 a i) has lost the larval form and 

 has now a distinct " shoulder" on the outer margin. The number of bristles on the exo- 

 pod has increased so that there are five on the outer margin and three on the inner. 



Thoracic appendages II-VIII. The exopods of Th. II-VI show more clearly the 

 articulation of the basal with the terminal part, and the natatory setae are increased in 

 number. Only Th. VI is figured (Fig. 26 a vi). The endopod of Th. II is shorter than that 

 of Th. Ill and there is a decrease in size from Th. Ill backwards. Th. VII (Fig. zGbvn) 

 is an inconspicuous process bearing two setae terminally and Th. VIII (Fig. 26 ^viii) 

 is a still smaller vestige which may or may not have a seta. Th. VII and VIII are 

 figured along with the gills belonging to these appendages. 



Gills. The gill or epipodite of Th. I (Fig. 26 b i) is similar to that seen in the 

 previous stage. The gills of the remaining thoracic limbs (Fig. 26 Z>ii-viii) are more 

 developed than previously, those of Th. II and III are five-lobed, Th. IV is also five- 

 lobed with indications of a further lobe developing. The gills of Th. V and VI are 

 similar in development to those of the preceding stage. The gill of Th. VII has four 

 well-developed lobes and two more short lobes developed in proportion to the size of 

 the larva: two diff"erent conditions of this gill have been figured. The gill of Th. VIII 

 has three large lobes and two small ones near the peduncle. 



Pleopods. There is an increase in the number of marginal bristles (Fig. 26 c i, ii, v) 

 and the appendix interna (Fig. 26 d) has four or five hooks. 



ADOLESCENT FORMS 



Rustad (1930, p. 68) gives reasons for the abandonment of the term "post-larval " to 

 describe the stages which succeed those formerly classed as Cyrtopia. He states that the 

 latter stages merge gradually into the adult and points out, what Dr Bargmann has also 



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