NO. 1788. -NORTH AMERICAN ERQASI LI DM— WILSON. 339 



Furthermore, in bodily structure and habits it comes as near to 

 being a golden mean between the extremes shown by other species 

 as could well have been selected. And being thus common, there is 

 far greater chance for the discovery of its life history than in the case 

 of a rarer species. 



These facts have combined to make it the best known of all species, 

 and nearly every European author who has dealt with the parasitic 

 copepods has at least mentioned it. 



Nordmann, whose description in other respects was singularly accu- 

 rate, contents himself with a mere mention of the mouth-parts. This 

 defect was amply remedied by Claus, who gave a detailed description 

 of these appendages, %vith excellent figures. The last author men- 

 tioned above, Gadd, has recently tried to assail this description given 

 by Claus; his opinions will be found discussed on page 279. 



Nordmann described only the female ; Kroyer tried to remedy this 

 by a brief notice of a form which he took to be the male. He tells us 

 first of all that the finding of the young and the males of E. gasterostei 

 induced him to make a search for similar specimens of E. sieholdii, 

 and that this search was rewarded by the discovery of half a score of 

 males among several hundred females. Many facts, however, com- 

 bine to prove that these specimens were not males, but simply females 

 without their egg-strings. 



1. The males have been proved to be free swimmers throughout 

 life, and the only chance of finding them among females taken from 

 fishes' gills would be in rare instances when the two are found in 

 union. Kroyer's percentage is far too large for anything of this sort, 

 and he makes no mention of finding the two sexes together. 



2. The "males" are represented as being of the^same size as the 

 females; this is possible, but not very probable, since the male usually 

 shows considerable variation in size. 



3. The "males" showed no sex characters whatever; the few 

 trifling difl'erences noted by Kroyer are what would be expected 

 between a young and a fully mature female ; but not one of them is 

 worthy of being made a sexual distinction. 



4. If they were really males, they should possess the large maxilli- 

 peds characteristic of that sex. But Kroyer's figures clearly show 

 that no such mouth-parts were present in his specimens. 



5. If the females of Kroyer's new species, longimanus, be compared 

 with these "males" of sieholdii, both being shown by Kroyer on the 

 same plate, there will be found so complete a similarity between the 

 two as to leave little doubt of their identity. 



Gadd (1904) found a single specimen which he considered to be a 

 male of the present species. And his claim seems just, for in this 

 instance the male was fastened to the body of a female, was con- 

 siderably smaller than the latter, and showed several decided sex 



