6o 



COPEPODA 



probably an indication of the final ecdysis. The mouth limbs are scarcely different from those of 

 mature females. The males are always easily distinguished from the females by the presence of the 

 well developed pes V (text-fig. 13 d) which consists of two basal segments and two terminal ones (Re), 

 which especially on the right side, are not always so well distinguished as figured by Canu (PI. II fig. 6). 

 In this stage varieties similar to those of mature females but less marked were found. 



Y. (Stage IV). Size: 0-9 1-4 mm. But for the presence of only 3 somites in the abdomen this 

 stage is like the preceding one, and shows similar differences between the two sexes (text-figs. 13 e f). 

 Y. (Stage III). Size: 07 1-0 mm. This stage, of which Stephensen has given figures of 

 all the limbs, shows no sexual differences, and is characterized by fcnir natatory legs and two abdo- 

 minal somites. 



Y. (Stage II). Size. 0-5 0-8 mm. This stage has three natatory legs and two abdominal 

 somites. The last copepodite stage as well as the larval forms was not with security found out; I 

 refer to O berg's description. 



Variation. From Iceland I have examined a female (taken *5/ 6 1902 by Ditlevsen in Heste- 



reyrifjorde) with a spermatophor attached to the genital somite, in which a fairly well developed 



fifth pair of legs was observed (cf. text-fig. 14 a b). 



The Ingolf Exp. (at St. 49 V. 1 100 o fm.) has taken 

 a full-grown female? alike the preceding but with 

 much longer pes V, of which the left is longer than 

 the right (text-fig. 14 c). The 0. Exp. 1900 (F. 451) 

 has taken a female with a right and left pes V of 

 almost equal length ; the Re III of left pair is rounded 

 and short, without terminal seta; the corresponding 

 segment of the right side is more elongate. From 



Ingolf (St. 29 V 1 50 o fm.) I have examined a 

 Text-fig. 14. Pserui. miutm Kr., abnormal female. y<JunR animal (??) ^^ & rudimentary pair of legs> 



a. Abdomen (female with spermatophor from Hestereyri- consisting of two short basal segments, and a rounded 

 fjord Iceland) x 67. 



b. Pes V of same specimen x 160. small terminal segment. Boeck is the first who 



c. (to the right) Pes v of specimen from ing. St. 49- has mentioned females with a fifth pair of legs 

 (1864 p. 234), and Mrazek has published an interesting study on this topic. He has found a small 

 rudiment now and then, and sometimes a fairly well developed pair of legs; his figures of two spec- 

 imens are somewhat different from each other, but in structure mainly like my specimen from 0. 

 Exp. Kr a ef ft has examined a female with a rudimentary fifth pair of legs. It is interesting, though 

 in no way surprising, that the organ in none of the 6 specimens in which its structure has been 

 described was alike another. 



Occurrence. This species has been taken almost all over the area explored by the Ingolf 

 Expedition, as far north as Jan Mayen and the Diskoisland; in the Atlantic it has not been taken 

 farther south than at the latitude of 63 North. By the East-Greenland Expedition it was only taken 

 at comparatively few stations, south east of the Faeroes 6io6 Lat. N. io26 Long. W., in the Nor- 

 wegian Sea as far east as io4 Long. East (lat. 62i6 North) and at 6i2 Long. West (at 69o6 Lat. 



