366 



DISCOVERY REPORTS 



N. = non-setose, s. = setose. 



Specimens found: stage 1 = 5, stage 2=1, stage 3 = 4, stage 4 = 20, stage 5 = 3, stage 6 = 0. 



Lebour (1949) has described three stages (the first three) of E. tenera from Bermuda. The first of 

 these carries one non-setose pleopod, the second four non-setose and one setose and the third five 

 setose. Only the third of these stages occurred in the series presented here. 



The larvae examined during this inquiry were considerably larger than those described by Lebour 

 (E. tenera is a small species) and in the first stages the state of development of the cormopods and 

 pleopods was relatively advanced. 



My material was preserved, and positive identification was therefore more difficult. However, these 

 larvae occurred in the same tows as adult E. tenera and later stages resembled the adult phase of 

 E. tenera (particularly in the shape of the rostrum) more closely than that of any other euphausiid 

 present. They conform closely to Lebour's descriptions and illustrations and the similarity in the 

 shape of the rostrum is most marked. The explanation of the discrepancies in the earlier stages may lie 

 in inadequate sampling (only thirty-three specimens were present in this material), and the first two 

 stages described by Lebour are, therefore, the real stages. Another possible explanation of the large 

 size and advanced condition of development may be found in the environmental differences en- 

 countered in the Benguela Current and the Bermuda waters. The Benguela Current is a cold, up- 

 welling current with waters rich in nutrient salts, whereas the warm oceanic waters of the north- 

 western Sargasso are notoriously poor in nutriment. 



First furcilia. Five specimens examined and measured. Length range 4-0-4-4 mm. ; average length 

 4-2 mm. (Fig. ija-j). 



The frontal plate of the carapace is rounded and comes to a sharp point in the centre of the 

 anterior margin. The margin is otherwise quite smooth. The inferior margin of the carapace carries 

 a small denticle toward the posterior end. Its posterior margin lacks a dorsal spine. 



There are three segments to the first antennal peduncle and the basal segment carries, on its outer 

 distal margin, a strong-toothed spine which extends to just beyond the distal end of the third seg- 

 ment. The third segment carries two rudimentary flagella. 



The second antenna is biramous and natatory. The simple endopod carries four setose spines 

 terminally and the exopod carries seven. 



The first and second maxillae are visible. The first and second cormopods are present and bifurcate 

 and the second carries rudimentary gill-lobes. The third is present as a naked, simple bud. 



The first abdominal segment carries a pair of setose pleopods and the following three carry non- 

 setose pleopods. 



The well-developed telson carries well-developed uropods. It is armed with one pair of ventro- 

 lateral, three pairs of postero-lateral, and seven terminal spines. 



Second furcilia. One specimen examined and measured. Length 4-9 mm. (Fig. 180, b). 



The anterior margin of the frontal plate is somewhat less pointed than in the preceding stage. 



