56 



COPEPODA 



though consisting of the same number of segments. Normann & Sco tt have with reservation described 

 a female with the right fifth foot three-segmented, and longer than the left as P.p. var. perplexus. 



Remarks. The specimens, which have been examined all belong to the northern variety (var. 

 borealis Wolfenden p. 997), and are fairly well distinguished from the Mediterranean form described by 

 Giesbrecht. A. Scott (1909 pp. 27 — 28) thinks that the differences are rather unimportant, in that 

 he is scarcely right. Detailed examination of a good many specimens from different localities especially 

 from the Mid-Atlantic is necessary to decide the question whether the observed differences are specific 

 or due other reasons. 



Occurrence. The Ingolf Expedition has taken this species from 7 stations to the south and 

 south-east of Iceland as well as in the Fseroe channel. It has been taken as far west as at St. 84 

 Long. W. 25°24, Lat. N. 62°58; the only station farther north where is has been taken by the Ingolf 

 Exp. is St. 101 (Apst. 47 9/ 7 1896 4 p. m. 66°23 Lat. N. i2°05 L. W. 2 f$) north-east of Iceland. From 

 the East Greenland Exp. 1900 it was once taken in Denmarks Strait as far north as 65°36 L. N. 3i°32 

 L. W. 9/ 9 2 a. m. F. 318. The comparatively few other localities, in which it has been taken by this 

 Expedition lies between 62°o6 Lat. N. and 59°20 L. N., and 2i°n L. W. and o°52 L. W. At the fol- 

 lowing stations more than single specimens of this species were captured. 



Ingolf *7/ 6 96 St. 84 62°58 L. N. 25° 24 L W. Cyl. 9 f ?; 3 y? (V); 2 ytf (IV). 

 *9/ 8 95 6i°02 L. N. o°4o L W. PI. 11 f?; 2 y c? (V). 



i7/ 8 96 6o°28 L. N. o°20 L E. Cyl. 9 f ?; 1 f <?; 3 y? (V); 1 yo* (V); 1 y'?(IV); 1 yo* (V). 



0. Exp. 1900 % 6 p. m. 6i°6 L. N. i6° 2 6 L. W. F.389 2 f?; 2 fj*; 6 y? (V); 2 y J* (V). 

 2 5/ 9 2 p. m. 6o°29 L. N. i2°io L. W. F.399 7 f?; 3 yj< (V). 



8 a. m. F.396 3 f?; 2 y? (V); 2y^ (V). 



It is an interesting fact that almost all the collections of this species are from the month of 

 September (0. Exp. 1900 9/ 9 — 3°/ g 16 Stations) or from the month of August (Ingolf Exp. 1895 — 96 

 9 /8— 17 /8 8 Stations). In the month of May a single young male (4/ 5 96 Cyl. 2 57°54 Lat. N. 6°27 L. E.) 

 was taken, and hi the month of July (Cyl. St. 84 r 7/ 6 1896 62°58 Lat. N. 25°24 Long. W.) 9 mature 

 females, 3 young females (stage V) and 2 young males (stage IV) were taken. Young animals (St. 

 IV — V) were also captured as late as 2 7/ 8 1896 and 2 ?/ 9 1900. The fact that this species was rarely 

 taken in several collections in the monthes of May and June 1895, 1896 and 1900 in the same regions 

 in which it was found in August and September indicates a certain periodicity in its occurrence, as 

 shown by Farran, in several of the localities explored by the International Investigations (1910 pp. 

 61—62). The average salinity for this species, which generally is swarmiug at the surface is rather 

 low in the Kattegat (19-33 %o, Temp. 10-33° C-)> but a good deal higher in the English Channel (35-26 %o, 

 Temp. 13-28° C). According to Cleve (1901) the salinity in the Arabian Gulf lies between 35-77 %o and 

 36-20 %o (Temp. 267 C.) and in 1904 between 35-40 and 40-70 % ; the maximum temperature at which 

 it was found in the Indian Ocean is 29°35 C. (Cleve 1901 p. 8). 



Distribution. Assuming the specific identity of the northern and tropical forms we find records 

 of its occurrence from the Mediterranean, the Black Sea, the Red Sea, the Arabian Sea, the Indian 

 Ocean as far South as New Zealand (Brady 1911 p. 32), the Malay Archipelagos (A.Scott 1909) the 



