9 8 DISCOVERY REPORTS 



lives mainly in shoals, and Limacina balea and Salpa fusiformis, though normally found 

 in small numbers, sometimes occur in exceptionally dense masses which may extend 

 over many square miles. Other species such as Parathemislo gaudichaudi and Calanus 

 simillimus are found only occasionally in abnormally large numbers, the majority of 

 specimens being taken in hauls of normal size. Other species again seem to have no 

 tendency to form any definite aggregations. This point will be dealt with more fully 

 when each species is separately considered in the following pages. 



The N ioo B analyses provide a large body of data on the distribution of the various 

 species, but separate species or groups will be dealt with in detail in subsequent pub- 

 lications, and the distribution of individual species will therefore be considered in the 

 briefest possible manner here. For the same reason, little reference will be made to 

 records of the occurrence of each species in the publications of other expeditions, for 

 if this were done the following notes would need to be greatly enlarged. Mention 

 should be made, however, of one or two papers which deal with certain aspects of the 

 distribution of the macroplankton in these waters. For example, Ruud (1932) discusses 

 in detail the general biology and distribution of the Antarctic Euphausiidae and the 

 connection between Enphaiisia superba and the distribution of whales. Further re- 

 ference will be made to this paper in a later section. Ottestad (1932) has treated the 

 principal species of Copepoda in a similar way. The substance of these papers does not 

 very much overlap that of the present paper, but, so far as their conclusions have any 

 bearing on it, they are mainly in agreement with the following notes. Rustad (1930) 

 has also published a paper on the identification and development of the southern 

 Euphausiidae, but deals only briefly with their distribution. 



Except where otherwise stated, the following notes are derived entirely from the 

 samples on which this paper is based. 



Diphyes antarctica. This species is confined to the colder parts of the Antarctic 

 waters, and its northern boundary in the area of the Falkland Islands Dependencies is 

 roughly a line running from the South Shetland Islands to South Georgia. It is usually 

 found in the vicinity of the pack-ice, or in water which has recently been covered by 

 the ice. It seems to be scattered very evenly through the regions which it inhabits, 

 appearing at each station in small numbers, and there have been no indications of any 

 tendency to form shoals or even to occur in definitely larger numbers than usual. 



Dimophyes orctica. This species is known to occur at least in sub-Antarctic, as well 

 as Antarctic water, but it is only in the colder waters of the Bellingshausen and Weddell 

 Seas that it appears in any quantities. Here it is quite plentiful, but in warmer regions 

 it is rare. Its distribution is more "patchy" than that of Diphyes antarctica, but it 

 cannot be said to occur in shoals. 



Pyrostephos vanhoffeni. Recorded from time to time everywhere from the Antarctic 

 convergence to the most southerly stations of the Bellingshausen and Weddell Seas, 

 but it is definitely commoner in the colder than in the warmer parts of the Antarctic 

 water. It is curious that it seems to be absent from the coastal regions of the South 



