CAUSES OF PATCHINESS 237 



suggesting strongly that at times at least it must congregate, densely concentrated, at or near the 

 surface. Nemoto himself (1959) concludes that from the 'dominant appearance' of T. macrura in the 

 stomachs of some whales it must form ' large swarms in the sea ', and it must be to surface swarms 

 that he refers, for nowhere in his recent account of the feeding habits of baleen whales (Nemoto, 1959) 

 does he suggest that the southern species are anything other than surface feeders. We may include too 

 in this category Eiiphausia vallentini, the small krill reported to be eaten by the ' Pigmy ' blue whales 

 recently discovered (p. 48, note i) near Kerguelen. As for other southern plankton forms, outward 

 inspection of our specimen jars alone is enough to show repeatedly that the large tomopterid, 

 T. carpenteri, the calanoid, C. propinquus, the amphipod Parathemisto gaiidichaiidii, the pteropods, 

 Limacina balea and Cleodora sulcata and the salp, Salpa fiisiformis aspera,^ to mention only a few of the 

 more obvious cases, are all species that tend to be massed in enormous numbers on the surface, and 

 massed, moreover, to all appearances discretely in swarms. 



Hardy and Gunther (1935, Figs. 131-5), from their consecutive net hauls off South Georgia, 

 have already demonstrated the extreme patchiness of some of these forms and of several others I have 

 not mentioned, their results strongly suggesting that it is in surface swarms, each, as the krill swarms 

 seem to do, behaving very much as a single organism, that many plankton animals exist in the sea. 

 The truly remarkable patchiness they demonstrate in Parathemisto gaudichaudii,^ at two widely 

 separated stations where consecutive nets were used, leads us strongly to suspect that this is in fact 

 how they live. 



In his massive account of the plankton of the Gulf of Maine, Bigelow (1926) gives many instances 

 of conspicuous swarming at the surface by plankton animals. The following are among the more 

 striking: 



RADIOLARIANS Copepods 

 Acanthotnetron sp. Calanus finmarchicus 



Temora longicornis 

 COELENTERATES Ceniropages typicus 



Hydromedusae Metridia lucens 



Melicertum campanula Amphipods 

 Staurophora mertensii Euthemisto bispinosa juv. 



Phialidium languidum Euthemisto compressa juv. 



Scyphomedusae Euphausians 



Cyanea capillata var. arctica Meganyctiphanes norvegica 



Amelia aurita Thysanoessa inermis 



Thysanoessa raschii 



Ctenophores Decapods 



Pleurobrachia pdeus Larvae of Cancer spp. 



Beroe cucumis p^g^^jj ^^^^^^ 



CHAETOGNATHS PTEROPODS 



Sagitta elegans Limacina retroversa 



Clione limacina 

 CRUSTACEA 



Cirrepedes APPENDICULARIANS 



Nauplius and Cypris larvae Oikopleura sp. 



^ Now Salpa thompsoni (Foxton, 1961). 



^ The recent discovery (p. 48) that this large pelagic amphipod contributes substantially to the diet of sei whales provides 

 further evidence that it congregates densely in surface swarms, Hardy and Gunther's results suggesting that such swarming is 

 equally a phenomenon of the daylight as of the night-time hours. 



