﻿COPEPODS FROM LAKE ERH HAI, CHINA — HSIAO 



193 



ever, show more scattering than in the case of the males. To analyze 

 further, the specimens are arranged in seven classes according to size, 

 with a class interval of 0.5 mm. (table 5). 



The mean of the ratios of width to length is calculated for each 

 class and listed in percent in column 3 for males and column 6 for 

 females. The mean value for the male population is 63.45 percent 

 and for the female population 64.92 percent. To test the hypothesis 

 suggested by the above curves in figure 28, namely, that width and 

 length show isauxesis, and hence variations in the mean values of the 

 ratios between width and length in different size classes have occurred 

 by chance, the chi square (x^) test is applied to these data. In col- 

 umns 4 and 7 the difference betvreen observation and theoretically 

 expected values is listed for males and females respectively. From 

 these the chi square is calculated by the usual method. Its value for 

 males is 0.029, which corresponds to a P>0.99 in Fisher's table for 

 chi squares (x"). In the case of females, chi square (x') =3.508, P 

 is 0.75. In neither case is the difference in the means of the width/ 

 length ratio significant. In the males, as Avell as in the females, the 

 width increases isauxetically with increase in length. 



Table 6. — Comparison of carapace and abdomen of male and female argulids 



Character 



1. Carapace: 



Range of length 



Mean of length. 



Standard deviation 



Standard error of mean... 

 Coefficient of variation. . _ 



Range of width/length. . . 



Mean of width/length 



Standard deviation of 



width/length. 

 Standard error of mean... 

 CoeflBcient of variation... 



2. Abdomen: 



Range of length 



Mean of length 



Standard deviation 



Standard error of mean... 

 Coefficient of variation... 



Range of width/length 



Mean of width/length 



Standard deviation of 



width/length. 

 Standard error of mean.. 



Coefficient of variation 



Male 



2.8-3.5 mm 



3.065.. 



0.198 



0.044 



6.45 percent 



88.6-101.1 percent 



93.02.. 



3.230 



0.722 



3.47 percent 



1.03-1.25 mm 



1.127 



0.067 



0.015 



5.98 percent 



63.6-81.1 percent. 



71.13 



4.698 



1.05 



6.59. 



Female 



2.53-3.62 mm 



3.14 



0.271 



0.06 



8.62 per cent. 



84.7-102.5 percent 



92.0 



4.712 



1.054 



5.12 percent 



0.72-0.995 mm.... 



0.966 



0.092 



0.20 -. 



9.56 percent 



41.2-68.0 percent. - 



66.62 



9.171 



2.05 



16.2 



Diflerencc 

 9-d' 



0.075 mm. 



2.17 percent. 



—1.02 percent... 



1.65 percent 



—0.161 mm 



3.58 percent 



—14.51 percent.. 



9.61 percent 



Stand, error 

 of difference 



0.0075 mm. 



1.22 percent. 



0.0255 mm. 



2.304 percent. 



