Euphausiidæ. 31 



very short. The antennæ and oral parts scarcely exhibit 

 any perceptible difference from those parts in the 1st stage. 

 The metasome, on the other hand, has considerably in- 

 creased, so that it now exceeds in length the anterior divi- 

 sion, and its 5 anterior segments are distinctly marked of 

 from each other, whereas the 6th segment is still confluent 

 with the telson. In the short body-section lying immediately 

 in front of the metasome, and which is explained above as 

 the mesosome, a very slight but dense transversal striation 

 may be traced, indicating an incipient segmentation of this 

 part, and ventrally, just behind the maxillipeds, a small 

 rounded tubercle has appeared filled, with a cellular matter, 

 which is the fundament from which, in more advanced 

 stages, the 1st pair of thoracic appendages (legs) will develop 

 themselves. The several internal organs appear in this stage 

 still more clearly through the pellucid integuments. 



Last Calyptopis-stage. 



(PI. 4, figs. 4—13). 



Though the larva, on attaining this stage, has con- 

 siderably increased in size, measuring now about 2y 3 mm. 

 in length, it looks very like that in the 2nd stage, as de- 

 scribed above, and it is only on a closer examination that 

 it is found that some more essential changes have taken 

 place. The body (see fig. 4), on the whole, appears some- 

 what more slender, the metasome especially being more 

 fully developed. The carapace has preserved its form 

 nearly unaltered, though, seen laterally, its upper face 

 appears somewhat less vaulted, and its anterior extremity 

 more sharply angulated. At the postero-lateral corners a 

 distinct tooth-like projection has appeared, showing the 

 larva to belong to Nyctiplianes norvégiens, in which form a 



