3'6 



DISCOVERY REPORTS 



deep water. In the night series, Table LXII, nine out of the sixteen stations have a depth 

 of over 500 m., and here we see a considerable difference in the numbers taken over 

 deep water in the case of Euphausia superba, E. frigida, Salpa fusiformis and to a lesser 

 extent Thysanoessa spp. The grazing effect of some of the macroplankton must indeed 

 be heavier over the deep water than in shallow water. The principle, illustrated in 

 Fig. 168, must thus be one of some ecological importance. In Tables LXIII and LXIV 

 showing the smaller animals, particularly the Copepoda, we notice only a few significant 

 differences between deep- and shallow-water stations, e.g. Foraminifera in the daylight 

 but not the night series, the deep-water Copepoda Scolecithricella minor and Metridia 

 gerlachei in both series. The neritic nature of Drepanopus pectinatus is clearly shown. 



Table LXII 



Showing the average numbers of the more important macroplankton organisms taken in the 

 series of three N 100 H nets at each night station; the stations being arranged in order 

 of decreasing soundings from deep to shallow water 



* Bottom not reached. 



It is necessary to consider this matter in detail because it does appear at first sight 

 that here is a possible alternative explanation of some of the phenomena we have ob- 

 served. We must once again see if there are correlations with phosphate values, but this 

 time split the series into shallow- and deep-water stations. Let us consider the N 100 H 

 nets first. In the shallow-water series we have eight stations in water of phosphate 

 value > 100 mg. per m. 3 , one of which is a night station, ten stations in water of phosphate 

 value 90-100 mg., three of which are night stations, and twelve stations in water of 

 phosphate value < 90 mg., three of which are night stations. Here we can include the 

 night stations, since there are as many in the low phosphate range as in the intermediate. 

 In the deep-water series there is only one station of phosphate value below 90 mg. 



