INTIMATE STRUCTURE OF THE SWARMS 251 



By means of this apparatus we are investigating whether the structure of a patch is in any way orderly Above 



all, we are considering the food availability in the interior of the swarm, and the varying distribution of sex-ratios 

 and developmental stages. 



In this way the form and internal structure of a larval swarm might perhaps be accurately mapped 

 together with the form and internal structure of adjacent swarms and the distances separating them 

 from each other. We already indeed find that such swarms, in so far as their stage frequencies go, are 

 anything but disorderly. 



1 I I [ 1 1 r 



DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT 



NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT 



T 1 f 1 1 r 



NOV DEC JAN FEB MAR APR 



Fig- 54- Growth curves of E. superba after Ruud and Bargmann. 



GROWTH AS INDIVIDUALS AND SWARMS 



As INDIVIDUALS 



In illustrating the growth-rate of plankton animals, it is customary to plot the average monthly or 

 half-monthly length of as large a series of measured specimens as possible. Thus Ruud (1932), mainly 

 from specimens collected from whales' stomachs, and Bargmann (1945) from specimens collected 

 from the plankton, obtain the growth curves reproduced in Fig. 54. Before one year's growth 

 is over, when the adolescents (p. 339, Fig. 95) first appear in substantial numbers in August, 

 Bargmann is able to distinguish between males and females and accordingly from August onwards 

 her growth curve divides into its male and female components. As Fig. 54 shows the growth- 

 rate in the two sexes is very similar, the two curves, although the females are consistently smaller than 

 the males,! following approximately the same course. Ruud does not treat the sexes separately and 

 since he only had substantial larval samples for January, and little or no larval material covering the 

 rest of the year, his curve for the greater part of the first year's growth is largely conjectural, and, as 

 Bargmann (1945, p. 123) points out, in its early stages at any rate, much too steep. In certain broad 

 essentials, however, the two curves agree, both showing at the end of the first year the increase in 

 growth that accompanies the spring blooming of the phytoplankton and both a distinct slowing up 

 1 See again, however, Fig. 53 which clearly suggests that in a final burst of growth the female overtakes the male. 



28-2 



