DEVELOPMENT OF E. VALLENTINI 271 



Fifth limb. Endopod of five segments, not kneed or kneed. 



Sixth Hmb. Very rarely short, bifurcating and with endopod non-setose; usually 

 longer or long with endopod setose and of two to five segments. 



The first pair of gills may or may not be present as very small buds. Most frequently 

 the second to fifth pairs are not branched or just beginning to branch, the sixth two- 

 branched, the seventh and eighth three-branched. They may be less well developed: 

 the second to fifth single, the sixth to eighth just beginning to branch ; or the second to 

 fifth single or just beginning to branch, the sixth and eighth two-branched, the seventh 

 three-branched. They may be further developed: the second to fifth beginning to 

 branch, the third more advanced than the second and so on, the sixth and seventh three- 

 branched, the eighth four-branched ; or the second to fifth as in the previous clause, the 

 sixth three-branched, the seventh and eighth four-branched. 



The tergal wings are not connected dorsally by a collar. 



Development of Euphausia vallentini 



No one has described any of the larval forms of E. vallentini. The following is a list 

 of those that I have examined, with the numbers of each : 



Calyptopis: Second 



25 



50 



Third 



Furcilia: 



Stage I. With 4 pairs of non-setose pleopods ... ... ... ... ... ... 62 



With 3 pairs of setose, 2 pairs of non-setose pleopods ... ... ... ... 3 



Stage n. With 4 pairs of setose, I pair of non-setose pleopods ... ... ... ... 47 



Stage in. With 5 pairs of setose pleopods, antennal endopod unsegmented ... ... 135 



Stage IV. With antennal endopod segmented, 5 terminal spines on telson ... ... 20 



With antennal endopod segmented, 4 terminal spines on telson ... . 12 



Stage V. With antennal endopod segmented, 3 terminal spines on telson ... ... 93 



With antennal endopod segmented, 2 terminal spines on telson ... . . 15 



Stage VI. With antennal endopod segmented, I terminal spine on telson ... ... iii 



All came from immediately north of the Antarctic convergence between the Falkland 

 Islands and South Georgia, i.e. from one sector of the sub-Antarctic Zone and from 

 near the southern limit of the habitat of the species. 



The larvae of E. vallentini are so similar in general appearance to those of E. frigida 

 that they would be indistinguishable from them were it not for the dorsal organ of the 

 carapace in all the stages described here, and the "tergal collar" of the Furcilia stages 

 II-VI. 



Second Calyptopis (Fig. t,"] a,b) 



Description based on the examination of twelve specimens. Twenty-one were measured and were 

 I-6-I-8 mm. long. 



The carapace is similar to that of the same stage of E. frigida except that there is 

 mostly, but not invariably, a small but distinct dorsal organ. 



The appendages are as in the second Calyptopis stage of E. frigida, and the thoracic 



