324 



DISCOVERY REPORTS 



it was present in only i-6%, whereas it was present in 67-9% of similar hauls taken during the night. 

 It is also clear from Table 3 that on the few occasions it has been taken in the upper 100 m. during the 

 day it has only been present in small numbers, the mean number per haul, considering positive hauls, 

 only being 2-8; the corresponding figure for night hauls is 13-8. 



Fig. 9. The daily vertical distribution of adolescent and adult E. triacantha. A, the mean number per 20 min. N lOoB haul 

 in the upper 100 m. for each 2-hourly period. B, the mean number per 20 min. N 100 B haul between 250-100 m. for each 

 2-hourly period. C, the mean number per 250 m. N70V haul for each 4-hourly period. Cross-hatching indicates means 

 based on only one specimen. (See Table 5 for the number of observations on which this figure is based.) 



The diurnal variation in the numbers in the surface water could be caused by a diurnal variation 

 in avoidance of the net. However, it is shown below (p. 328) that there is no such difference between 

 day and night avoidance, and consequently this must be a real variation in the population and not 

 just an apparent one due to the sampling methods. 



Fig. 9 A and B shows the mean number of adolescent and adult E. triacantha per 20 min. loo-o m. 

 and 250-100 m. hauls, respectively, for each 2-hourly period. Only those stations have been used at 



