96 



DE. a. H. FOWLEE— BISCATAX PLANKTON 



markedly showed mucli the same avoidance of the surface as was noticeable with Sagifta 

 serratodentata (p. 61, supra). Both sets of figures include day and night hauls; the 

 swarm-hauls 21 eto h (21 i was with net 18) are also included : — 



c 

 o 



10 

 9 

 10 

 10 

 19 



C3 f-" Q 



but; s 



'5 

 a. 



3 

 3 

 3 

 1 

 9 



5-. CJ ^ 



O ^ o m 



X** jj o > 



s- cd 2^ ^ 



= '" faC O 



I ^ 





a 



S 



u 

 <u 



"Were the swarm-hauls omitted, the dry-weather values for 0, 50, and 100 fathoms 

 would be 10-4, 6'8, and 2-1 ; and the contrast would be even more marked. 



In the following table the swarm-hauls have been omitted, in order to get an idea of 

 the vertical distribution of these blastozooids irrespective of swarms : — 



At 



25 



50 



75 



100 





2 S 



^ O 



41 



58 

 83 

 72 

 55 



o 



a 



o 



o 



60 



7-8 

 2-3 

 10-3 

 2-8 

 2-6 



\ 



; 



a; o 



" ^- 



too "» . 



CS C ^ 



S-. <u ;; 



<" p S 



Both percentages of hauls and average specimens per hour indicated that 50 fathoms 

 was the optimal horizon *. 



Average lengths per depth, w^hen tabled, did not show that older specimens sought a 

 different level from the younger specimens. 



We may summarize the foregoing paragraphs as follows : — The captiires, as a whole, 

 yielded no evidence for or against a day and night oscillation; but they markedly 

 indicated an avoidance of the surface during or after rain, the species becoming most 

 plentiful at 25 and 50 fathoms ; the average expectation of specimens is highest at 

 50 fathoms, which may be taken to have been the oi)timal horizon for the date and 

 area studied. 



In epiplankton hauls at or abov^ 100 fathoms these blastozooids occurred in 65 per 

 cent, of the total havils ; below 100 fathoms they vanished; on three occasions only 

 (cf. Table, pp. 100-101) there were taken in the mesoplankton net from considerable 

 depths fragments of very large specimens of a blastozooid, mostly larger than any of 

 the epiplankton specimens. These may have been dead specimens of Blastozooid A, 

 or may even possibly belong to a deep-water species. But there can be no doubt that 

 Blastozooid A is epiplanktonic. 



* It is curious that, on -whatever principles such statistics are arranged, the average specimens at 50 fathoms 

 always have much higher values than at 75 and 25 fathoms. The same was observed in Sagitia serratodentata. 



