278 



DE. G. H. rOWLEE — BISCAYAN PLANKTON : 



their curve (fig. J) shows that they all helonged to one stage. At least four, probably 

 five, stages in all were reiiresented. 



The actual observations were as follows : — 



Table R. — Total specimens measured : 315 ? + 1 (J = 31G. 



Stage I. shows a solid, hut markedly asymmetrical curve, if the ordinates are simply 

 joined ixp. Stage II., on the other hand, shows a douhle-humped curve (for which no 

 morphological reason appeared), and tlie lower part of the curve of Stage I. could 

 without violence he resolved into a double hump. It is conceivably possible that these 

 abnormalities in the curves may he connected with the rarity of males, if there is any 

 truth in the suggestion on p. 308 that parthenogenesis may occur in this species, since a 

 parthenogenetically produced race often difi'ers markedly in structure and size from 

 a sexually produced race. 



Considering the scarcity of the smaller specimens, the response of the mean to Brooks's 

 law is good:— 0-37 X 1-62 =0-59; 0-59xl-62 = 0-95 ; 0-95xl-02 = r539 ; r54xr62=2-49. 



The preponderance of Stage I. over the earlier stages is unusual, but the same was 

 shown by imbricata. 



Owing to the few observations at Stages III., IV., and V., only the two oldest can 

 safely be tested for the extremes of the curve; and respond well :— 2-S^l-62=l-7 ; 

 21^1-62=l-2. 



