STUDIES ON THE SECONDARY SEXUAL CHARAC- 

 TERS OF CRAYFISHES: III. MALES WITH 

 SUPERNUMERARY MALE SECONDARY 

 SEXUAL CHARACTERS IN THE 

 SUBGENUS FAXON I US. 



C. L. TURNER 

 ZOOLOGICAL LABORATORY, BELOIT COLLEGE. 



In the genus Cambarus the males of the subgenus Cambarus are 

 distinguished from the males of the other subgenera by the 

 presence of copulatory hooks upon the third segments of the third 

 and fourth walking legs. The other subgenera possess these 

 copulatory hooks only upon the third walking legs. These hooks 

 are secondary sexual organs and are used to some extent in the 

 process of copulation. It has been supposed that the number was 

 quite constant and the few specimens that have varied from the 

 normal condition have been classed as "freaks." Ortmann l in 

 discussing the use of the copulatory hooks as diagnostic features 

 says of Cambarus virilis and of Cambarus propinquus ". . . 

 always only the third pereiopods with hooks, barring freaks." 



A large number of individuals, indeed, enough to constitute a 

 considerable proportion of a crayfish population have been found 

 in Cambarus virilis and in Cambarus propinquus to deviate from 

 this rule in the possession of more than one pair of hooks. These 

 specimens can scarcely be classed as freaks. The deviation 

 becomes the more interesting since it occurs in a crayfish popula- 

 tion which has a large proportion of other aberrant conditions in 

 the secondary sexual characters such as the occurrence in females 

 of male secondary sexual characters, the occurrence in males of 

 female secondary sexual characters and the occurrence in females 

 of extra female secondary sexual characters. 



The thirty-two specimens to be described have been taken with 

 the exception of three from the lakes and streams of Wisconsin, 



'Ortmann, A. E.. 1905, "The Mutual Affinities of the Species of the Genus 

 Cambarus and Their Dispersal Over the United States," Proc. Amer. Phil. Soc., 

 Vol. 44, pp. 91-136. 



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