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PROCEEDINGS OF THE NATIONAL MUSEUM 



straight and diverge continuously from each other, the middle part 

 of this sinus is measured. 



The size of the males ranges from 1.72 to 4.99 mm. and of the 

 females from 2.12 to 5.09 mm. The size distributions of males and 

 females are shown in figure 27, A and B. The cumulative percentage 

 curves of both sexes are shown in figure 27, C. The percentage of 

 individuals of each class, with class interval of 0.5 mm., is plotted 

 against size class in the histograms. The model class among the males 

 as well as the females is 3.5 mm. (3.25-3.75 mm.) in total length. 

 From the cumulative percentage curves it will be seen that half of 

 the individuals are longer than 3.25 mm. 



Table 5. — Analysis of imdth /length ratio in male and female argulids 



The ratio between maximum length and maximum width has been 

 determined for each individual. The mean value of this ratio in 

 the male population is 63.45 percent, in the female population 64.92 

 percent. As this ratio among males varies from 64.7 to 69.3 percent 

 and among females from 4.66 to 83.8 percent, it would be interesting 

 to find out whether, by making use of the relationship y=hx^'\ proposed 

 by Huxley, the increase in the width (change of y) with respect to 

 growth in total length (change in cc) is heterauxetic or isauxetic. In 

 Figure 28, A, the log. of width is plotted against the log. of total 

 length for all the males and a straight line with a slope = 1 is drawn 

 through the points. The points all fall close to this line, suggesting 

 that length and width of Argulus japonicus grow at the same rate. 

 In Figure 28, B, the same is done for all the females measured. The 

 line with slope =1 also shows the trend of all the points which, how- 



