320 DISCOVERY REPORTS 



Appearance of adult males. The small proportion of adult males in the catches of 

 oceanic copepods is well known. Ottestad (1932) and Wolf enden (191 1) drew particular 

 attention to the absence of the mature male from the collections of Calamis aciitus made 

 by the ' Vikingen ', ' Discovery ', ' Gauss ' and ' Belgica '. Several authors, however, have 

 found that at certain short periods during the year the proportion of male to female 

 adults suddenly increases very greatly. The period of increase is followed by a much 

 longer period during which males are almost absent or present only in small numbers. 

 This sudden appearance of males was usually found to precede the appearance of 

 nauplii and young stages, and to follow or coincide with the appearance of females with 

 ripe eggs in the oviducts. Thus S0mme (1934, p. 77) found males of C. hyperboreus 

 "only exceptionally outside the period 15. xii to 15. ii, but within that period even a 

 short time with a surplus over the number of females. . . . Towards the end of the time 

 when females with eggs in the oviducts are found, that is to say just before spawning, 

 they (male adults) are already found to be present in very small numbers." Scimme ex- 

 pressed the opinion that the adult male has a very short life period, perhaps less than 

 two months. Farran (1927) also found males of C . finmarchicus in excess of females only 

 during the month of January, but a fairly high proportion also during May. He was 

 unable to relate their appearance to that of ripe females. Ruud (1929) found a high 

 proportion of adult males of C. finmarchicus present in May 1926 and 1927 at a number 

 of stations taken off the coast of Norway between February and July of those years. 

 Their appearance preceded the May- June spawning. Paulsen (1909) found large num- 

 bers of adult male C . finmarchicus appearing in June off Iceland, in sharp contrast to the 

 small numbers taken in the preceding and following months. He correlated their ap- 

 pearance with the spring period of reproduction. 



Table Y a-c and Fig. 18 show the percentage of males among the adults of Rhin- 

 calonus gigas taken in the Falkland Sector during the seasons 193 1-2 and 1932-3. Those 

 stations at which the number of adults was too small to give true percentage figures have 

 been omitted from the figure and are placed in brackets in the table. A few stations 

 taken in April in the south Indian Ocean have also been included in the table and in the 

 figure. In the season 193 1-2 the proportion of males rose suddenly in the middle of 

 December from a maximum of less than 10 per cent of the adults in the catch, and an 

 average of less than 5 per cent, to a maximum of 32-8 per cent. The figure suggests per- 

 haps that the proportion of males decreased more slowly than it increased and continued 

 high throughout December. In the season 1932-3 the proportion of males to females 

 increased more slowly from early in November and reached its maximum in the first 

 week in December, continuing high throughout that month. The appearance of adult 

 males thus coincides with the time of shedding of the eggs — so far as that can be fixed 

 from the scanty data available. It will be seen later (p. 326) that nauplii made their 

 appearance in the catches in the season 1931-2 in the middle of December, when adult 

 males reached a maximum, so that fertilization, shedding and hatching of the eggs must 

 take place within a very short time. It is not possible to know when the nauplii taken 

 in the middle of December were spawned, but it seems unlikely that they represent the 



