Figure 3. --Distribution of mean length by group and cruise. 



a> i2« 



Bo4t lenftii UM) 



Figure 4. --Length frequency 

 of the samples measured at 

 the Makurazakl fish market. 



both June and July correspond to group A; if 

 we try to compare them with the composition 

 of group B, as shown in figure 2, we see that 

 their positions are notably displaced to the 

 left. 



A Consideration of the Gradient and the 

 Source of Migration 



For a close relationship between 

 nonuniformity of the population and locality, 

 such as was discussed in the preceding section, 

 the usual mechanism that would come to mind 

 would probably be to relate it to the source of 

 the migrations of the schools. As can be seen 

 in figure 3, in June and July the schools clearly 

 show a northward movement. It is thought that 

 these schools probably continue to move north 

 through the spring and summer, so it is as- 

 sumed that in June and July they are engaged in 

 this northward movement. As they proceed 



42 



