SYSTEMATIC AND BIOLOGICAL ACCOUNT 127 



Mackintosh (1934) classed D. arctica as one of the species typical of the coldest Antarctic regions 

 such as those of the Bellingshausen and Weddell Seas, where it was plentiful, and said that it rarely 

 or never approaches the convergence. He gave the average number of anterior nectophores per haul 

 between the mean summer isotherms — i-oo° to - 1-99° as 14-4, and between similar isotherms 6-oo' J 

 to 6-99° as 1-40. 



Compared with an abundant Antarctic species like Calanus acutus (1900 per haul) Mackintosh 

 found that Dimophyes arctica was only moderately abundant in the Antarctic (1-90 per haul). 



io 1 - 



I2 V 



I4 U 



I5°C. 



Number of times recorded temperature is 

 minimum possible. 



: i 



Number of times recorded temperature 15 

 maximum possible 



Text-fig. 64. Frequency of capture of Dimophyes arctica in water of known upper and lower limits of temperature by 

 'Discovery' closing-net hauls. Black tally-marks show (upper series of columns) the number of times that the indicated 

 temperature was the minimum in which the specimens could have been taken ; and (lower series) how often the temperature 

 was the maximum possible for the same group of hauls (in). Superimposed, in the form of open circular tally-marks are 

 some of Bigelow & Sears (1937, fig. 81) records (53) for 'Meteor' closing hauls that yielded this species (six of their records, 

 covering temperatures ranging from 16 to 26 C, are omitted). The class boundaries used in the two sets of records are 

 staggered by half a degree Centigrade. The reason for giving two series of columns is that each closing-net capture was made 

 at an unknown depth in limited columns of water whose upper and lower levels were at different temperatures. 



In June 1952 'Discovery II ' took D. arctica in closing-nets in the North Atlantic at Stations 2927, 

 2929 and 2935 at depths between 1500-100 m., 1000-750 m. and 750-500 m. Dr Cooper informed me 

 (in lit.) that the mean temperature at Station 2929 (44 N., i5°W. approx.) for depths between 

 746 and 977 m. was 10-19° C, and that tne water was 'Mediterranean' or 'Gulf of Gibraltar' water, 

 formed in the Atlantic west of Gibraltar by mixing of warm, deep, saline water from the Mediterranean 

 with North Atlantic central water. D. arctica is not known to occur in the Mediterranean. 



Chelophyes appendiculata (Eschscholtz), 1829. (Plate IV, figs. 1,3.) 



Although this is one of the most common Siphonophores it was, until lately, the only common 

 diphyid that could not be associated in preserved plankton collections with an eudoxid. As Moser 

 (1925) said, that there should still be doubt on this point was difficult to believe. But Bigelow, 



