112 DISCOVERY REPORTS 



Rustad admits that he has not sufficient material to get a trustworthy idea of the dis- 

 tribution of the eggs and points out the Hmitations due to making only two vertical net 

 hauls — the lower from 400 m. — in the interpretation of his results. 



If eggs of E. superba occur in abundance in the proximity of drifting ice, it is rather 

 surprising that so very few have been taken over a period of four years in the surface 

 nets at stations made by the vessels of the Discovery Committee at the edge of, or actually 

 in, pack-ice. Many of these stations were made at a time of year when E. superba is 

 known to spawn, and if the number of eggs at St. 540, for instance, is typical of a spawn- 

 ing region the eggs could not fail to have been conspicuous in the plankton of the surface 

 nets. 



From discussion with Dr T. J. Hart it is learned that in his examination of the samples 

 analysed for his Phytoplankton Report (Hart, 1934) he did not find any eggs recog- 

 nizable as belonging to E. superba. The samples were from 50-cm. vertical nets (N 50 V) 

 fished from 100 m. to surface, and, as the Report eff^ectually demonstrates, used very 

 frequently and over a wide area in the Antarctic. This indication of distribution of eggs 

 in other than the first hundred metres, although admittedly negative, is based on such a 

 large number of observations that it cannot be neglected. 



Evidence in favour of deep spawning, additional to that supplied by the vertical dis- 

 tribution of the eggs themselves, is the occasional occurrence of fully adult animals in 

 the deep hauls of the 70-cm. vertical nets. It should be emphasized that this net, like 

 others, is selective in its fishing, and it is unusual to find adults of E. superba in it at any 

 time. That they should be found deep down at the same time as eggs are taken, as in- 

 dicated in Table III, leads one to infer that their occurrence at these depths is connected 

 with spawning. Their condition as regards maturity also indicates that departure from 

 the surface is associated with the deposition of eggs. The capture, referred to on p. 17, 

 of ninety-five adults including many gravid females in a 250-100 m. haul lends still 

 further support to the hypothesis of deep spawning in this species, and the fact that they 

 were the only adults to be taken in any of the vertical or oblique nets hauled at this 

 station is in favour of Rustad 's idea that the animals congregate in circumscribed shoals 

 for spawning. 



It is remarkable that comparatively few eggs have been found in the samples analysed, 

 and although Rustad 's suggestion of circumscribed shoaling "and the consequent con- 

 centration of the eggs in relatively small areas " may be partly the reason I do not think 

 that it is completely satisfactory. E. superba must be reproduced in immense numbers 

 to hold the key position it has in the ecology of Antarctic life. The yield of the 70-cm. 

 vertical nets, with the possible exception of those at St. 540, is surely not indicative of 

 the normal concentration. 



Is it possible that the development of eggs of E. superba takes place in water which is 

 deeper than the lower limit of the vertical nets and that the eggs obtained are the 

 scattered product of dispersal of a much greater mass situated in still deeper water.? 

 It may be that in this species the eggs, when laid, usually sink below 1000 m., and that 

 the great abundance at St. 540 is due to the net coming within 10 m. of the sea-bottom 



