28o DISCOVERY REPORTS 



second reason for selecting this species for investigation is its large size. The adult is 

 8-0-9-0 mm. in length, and the young copepodite stages are large enough to be taken 

 by the stramin net. As a general rule the young stages of nearly all the species of 

 macroplanktonic copepods are so small that they escape through the meshes of the i-m. 

 net. The young copepodites of Rhincalamis gigas, however, in stage iii and older, were 

 easily retained and occurred constantly. Stage ii occurred rather less frequently and 

 nauplii and stage i occurred only, presumably, when present in great abundance in the 

 water. Some idea at least of the course of events during the life cycle of the species can 

 therefore be obtained from the catches taken with the towed i-m. net. 



The author is deeply indebted to Mr G. E. R. Deacon and to Mr F. S. Russell, 

 D.S.C., for much help and criticism. In the many hydrological problems which arose 

 during the course of this work the advice of Mr Deacon was invaluable. 



METHODS 



The stations at which the Copepoda from the i-m. nets were examined during the 

 seasons 193 1-2 and 1932-3 in the Falkland Sector, and during the winter months around 

 the Antarctic Continent, are shown in Figs, i a, b, 2 a, b, and 3 and Tables I a-c. 

 It will be seen that only a selection of the total stations taken have been dealt with. The 

 catches were examined from 70 stations in the Falkland Sector in the summer season 

 November 193 1 to February 1932 and 76 during the season October 1932 to March 1933. 

 During the circumpolar cruise, April to October 1932, the copepod catches were 

 examined from 108 stations. 



Whenever possible, as will be seen from the tables, two towings were made with the 

 I-m. stramin net, one using the net as a closing net and towing obliquely from as nearly 

 as possible 250 m. to as nearly as possible 100 m., and the other towing as nearly as 

 possible from 100 m. to the surface. Both the upper and the lower nets were always fished 

 for the same length of time at every station : the upper for 20 minutes and the lower 

 for 30 minutes. Two 70-cm. silk nets were also attached to the warp and towed through 

 the same depths, one in conjunction with each of the i-m. nets. This paper, however, is 

 concerned only with the catches obtained by the latter. All four nets (two i m. and two 

 70 cm.) were towed together on the same warp, and the messenger, which closed the 

 lower nets at about 100 m., was released after the two upper nets (loo-o m.) had been 

 taken on board. A Kelvin tube, attached to a stream-lined lead, was placed between 

 the two upper nets to indicate the depth from which they were towed, and a Bourdon 

 tube depth gauge was shackled to the end of the warp to indicate the depths between 

 which the lower nets were fished. This instrument also gave some indication of the path 

 of the nets through the water. (For further details of the nets and apparatus see Kemp, 

 Hardy and Mackintosh, 1929; Ardley and Mackintosh, 1936.) 



It will be seen from Tables I a-c and II a-c that the actual depths through which the 

 nets fished varied constantly and widely from the loo-o m. and 250-100 m. which were 

 aimed at in every case. The warp was always hauled in at a constant speed of 10 m. a 

 minute, and the speed of the ship when towing was kept as nearly as possible at two 



