DEVELOPMENT OF EUPHAVSIA SUPERB A 23 



short, tapering in lateral view and slightly bilobed in dorsoventral aspect. The posterior 

 margin (Fig. 3 e) is armed with twelve spines, of which the pair on either side of the 

 emargination are very short and incompletely separated from one another. 



The antennules are unsegmented and uniramous, bearing three long bristles at their 

 tips. The antennae (Fig. 3/) are biramous and also furnished with long bristles. The 

 mandibles are in this stage reduced and bud-like in appearance. Maxillae I and II are 

 rudimentary single-lobed buds, and the first thoracic legs are small bilobed processes 

 without setae. Anterior to the mandibles lies the labrum and posteriorly between the 

 mandibles and the ist maxillae the bilobed labium (Fig. 3 c). 



FIRST CALYPTOPIS 



The average lengths and the ranges of length for varying numbers of ist Calyptopis 

 are stated in Table VIII. The extreme range for 500 individuals from an oblique net 

 fished at St. 647 is between 1-33 and 1-92 mm. The frequency distribution of these 

 larvae is as follows: 



Length, mm. 1-33 1-38 1-41 1-46 1-50 1-54 1-58 1-63 1-67 171 1-75 179 1-83 i-88 1-92 

 Frequency 3 i i 3 7 19 41 51 78 62 78 73 67 15 i 



Their average length is 171 mm. The lengths of all the other larvae fall within the 

 limits of the stated range, as do the lengths of those examined by Ruud (1932, p. 47). 



The carapace is without teeth or projections (Figs. 4 «, ^). The median eye is present, 

 and anterior to it are indications of the compound eyes. The rudiment of the ocular 

 luminous organ can clearly be distinguished as a dark mass of fibres within the de- 

 veloping compound eye. There is also a pair of frontal sensory organs anteriorly. 



The appendages, with one or two small diff'erences in detail, are as described by Sars 

 (1885) in Nyctiphanes australis. The two sensory appendages on the antennules are 

 difficult to see in unstained specimens. The antenna (Fig. 4 c) is composed of a two- 

 segmented peduncle and, distally, an inner and outer ramus as in the Metanauplius. 

 In the mandible (Fig. 4 d) the dentiform projection between the dentate part and the 

 molar protuberance is present ; also, as in N. australis, the denticulated plate — the lacinia 

 mobilis. At the base of the projection, where the plate is inserted, there is a bunch of 

 setae surrounding it. The palp of the ist maxilla consists of two segments as mentioned 

 by Ruud (1932) ; it bears five spines as opposed to six in A^. australis, three being at the 

 tip of the distal segment and two on the inner margin of the proximal segment. The 

 inner masticatory lobe is furnished with seven spines of varying structure and the outer 

 lobe with three (Fig. 4 e). The larval exopod is as in Sars' description. The 2nd maxilla 

 (Fig. 4/) diff'ers only from Sars' description in having three instead of four bristles on 

 the terminal segment. The ist thoracic limb (Fig. 4^) differs from that figured by Sars 

 for N. australis in having a short bristle at the articulation of the exopodite and the 

 basipodite on the external margin. 



The posterior portion of the body, behind the wrinkling of the integument which 

 foreshadows the segmentation of later stages, is shorter than the anterior part. The 

 abdomen is furnished with a pair of spines situated m9rginally but rather ventrally about 



