﻿COPEPODS FROM LAKE ERH HAI, CHINA — ^HSIAO 



191 



Finally the question of the justification of erecting two species, A. 

 japoniaus and A. folidceus^ should be carefully considered. There is 

 more difference between the two European species, foliaceus and core- 

 goni (Meehean, 1937), than between the Oriental and American 

 species, japonieus, and the European species, foliaceus. It might be 

 asked : Is a single difference in male character of two very variable 

 species sufficient to validate both as separate species, which, though 

 apparently separate in geographic distribution, actually might, by 

 artificial agents, be mixed through transportation of the host fish'^ 

 A world-wide survey may be required to clear this point. 



% 

 20 



10 







20- 



10- 







MALES 



% 

 100 



80 



-60-1 



FEMALES 



40- 



20- 





-' . -^'t 



/ 



/ 





CUMULATIVE 

 % CURVES 



12 3 4 5 



LENGTH IN MM. 



2 3 4 5 



LENGTH IN MM. 



Figure 27. — Size distribution of Argulus japonicus from Erh Hai. 



This series of specimens collected from Erh Hai offers itself as 

 good material for a statistical analysis of the specific characters. 

 Among this population of 210 argulids collected while they were free- 

 swimming, 58.5 percent were males and 41.5 percent females. The 

 animals are measured under a dissecting miscroscope with a calibrated 

 ocular micrometer. The measurements taken are defined in figure 

 26. The width of the abdomen in the male is its maximum width, 

 which is at the anterior quarter ; in the female it is the width across 

 the abdomen immediately anterior to the base of the anal sinus. This 

 difference in measuring abdominal width is necessitated by the fact 

 that the two sides of the female abdomen are parallel at the middle 

 half, but the posterior quarter may be bent laterally beyond the true 

 maximum width during fixation. The maximum width of the pos- 

 terior sinus of the carapace is the maximum distance between the two 

 concave sides, but in the female, where the two sides are nearly 



