290 



DE. G. H. FOWLER— BISCAYAN PLANKTON : 



specimens. The slight rise in " average specimens per 100 fathoms " at 750-500 fathoms 

 has been noticeable in other species, and will be discussed later (p. 297). 



The following table gives the compar 



At 0-1 



100 



fathoms 

 tills species 

 occnrred in 



62 per ce 





 50 

 33 



sr, 



100 

 100 

 85 

 100 

 100 



it. of 8 hauls by day, with 

 nidit. „ 



ative prevalence by day and by night 



G 

 6 



7 



r. 



3 



7 

 9 

 8 



day, 

 night. 



day, 

 night, 



day, 

 night, 



day, 

 nisht. 



1-37 



000 



1-lG 



2-50 



8-57 

 38-50 

 lG-33 

 17-28 

 2-1.-88 

 M-50 J 



specimens 



per hour 



haul. 



At 50 or more fathoms the chances of capturing the species (percentage of hauls) 

 were approximately equal by flay and by night, and the greater number of specimens 

 was also below this depth both by day and night. The small but uniform excels of 

 specimens taken by night at 50, 75, and 100 fathoms over those taken at the same 

 depths by day seems to suggest a .slight nocturnal movement upwards of specimens from 

 the upper mesoplankton. 



The total numbers at the surface and 25 fathoms are so small that it does not seem 

 profitable to discuss the reaction to rain, &c. 



With the large numbers of specimens available it seemed advisable to ascertain 

 whether a particular stage exhibited a preference for any particular horizon in the 

 epiplankton. The following table shows under I., II., and III. the percentage of the 

 total specimens of that stage which was found at each depth; unlike the other tables, 

 this gives (for obvious reasons) the actual numbers observed, not multiplied by a 

 time-factor : — 



At 



This table gives an interesting but negative result, in that there seems to have been 

 no stratification according to stages ; all three stages were most plentiful at 100 fathoms, 

 and more so at 50 than at 75 fathoms. 



As with some other species which have been worked out on similar lines, the horizon 

 of 75 fathoms shows lower figures in the tables than are found at 50 and 100 fathoms. 

 The reason for this is still to seek ; but the observation is interesting, as contradicting 

 the suggestion (which has more than once been made to me) that greater numbers 

 at lower depths in the epiplankton are due to specimens caught while hauling the open 



