238 



DISCOVERY REPORTS 



Table 48. 



Vertical net hauls. The orders of abundance in which samples of E. superba Calyptopes 

 and certain copepods occur in the Antarctic surface layer 



Depth 



50-0 



100-50 



250-100 



Many years ago when I visited the Arctic I made the following note (Marr, 1927) on the oc- 

 currence of plankton at the surface during the daylight hours of the summer and early autumn of 

 1925- 



August 30th, 80° 13' N, 51° 34' E, i-metre cheese-cloth tow-net. Duration of haul, | hr. Surface. Surface temp., 

 28-8° F. 



Calanus, Amphipods, Medusae, Scyphomedusae, Gymnosomata (Clione) in large numbers; Clio innumerable. 

 The sea appeared to be very dirty and the net was brown with Algal debris, which on examination proved to consist 

 of many species of Diatomaceae and broken down vegetable (Algal) matter. The net was choked with it. It had a 

 sickly, horrible smell, as of rotting seaweed. 



September 9th, 78° 38' N, 36° 28' E, i -metre cheese-cloth tow-net. Duration of haul, | hour. Surface. Surface 

 temp., 34° F. 



Tens of thousands of Calanus and Clio ; Amphipods, Sagitta, Clione, in huge numbers ; and a perfect maze of 

 Medusae, Scyphomedusae, Pleurobrachia, and Beroe. 



As regards the larger surface animals, the Ctenophores, Pleurobrachia and Beroe, were constantly observed in the 

 still, crystal-blue water of the pack, particularly on calm days when the sun was brilliant and the temperature high. 



In the same note I wrote, ' On several occasions I have hauled in a [surface] net literally black with 

 thousands of the little Pteropod, Clio, and swarming with active Calanus '. This also refers to daylight 

 gatherings. 



I can, however, recall no occasion when we made comparable daylight gatherings in the Antarctic 

 when fishing conventional stern nets on the surface of the sea. In fact for our daytime surface observa- 

 tions I find repeatedly in our records the entry ' catch negligible, thrown away '. It may therefore be 

 significant (see p. 265) that these enormous Arctic gatherings were got from a sailing ship, unac- 

 companied by vibrational disturbance such as might be produced for instance by a revolving screw 

 or by dynamos or other machinery. I record these rough notes, made when first, as a naturalist, 

 I went to sea, because I believe that for long we have been putting too much trust in what seems to be 

 revealed by apparatus, and not enough in what we can actually see. 



It is probable that the swarms in which it seems so many of these animals exist keep discretely 

 apart in the sea. In other words, swarms of different species do not mix. If they did we should 

 expect to find in whales' stomachs heterogeneous collections of plankton animals and not, as we 



