STUDIES ON THE SECONDARY SEXUAL 



CHARACTERS OF CRAYFISHES. IV. 



MALES WITH TWO SETS OF 



SUPERNUMERARY MALE 



CHARACTERS. 



C. L. TURNER, 

 ZOOLOGICAL LABORATORY, BELOIT COLLEGE. 



In study number three of this series, males of Cambarus 

 propinquus and of Cambarus virilis which bore supernumerary 

 male characters were described. These supernumerary char- 

 acters were in the form of copulatory hooks ordinarily found 

 only upon the third walking legs but in these cases present also 

 upon the second or the fourth walking legs. In C. virilis the 

 extra hooks were confined to the second walking legs. In C. 

 propinquus the additional hooks were found upon either the 

 second or the fourth walking legs. It was predicted that in 

 C. propinquus, since either the second or the fourth walking legs 

 might function in carrying the extra hooks, specimens might be 

 found in which copulatory hooks would be present upon both the 

 second and the fourth walking legs. 



During the summer of 1924 large collections were made from 

 practically all the streams and some of the lakes of southeastern 



FIG. i. Diagram illustrating the arrangement of the copulatory hooks upon the 

 third walking legs of a normal male specimen. 



Wisconsin and in one stream three males of C. propinquus were 

 found which bore supernumerary copulatory hooks upon one 

 or both of the second and fourth walking legs. 



DESCRIPTION OF SPECIMENS. 



Specimen number one (Fig. 2) is a male of the first form and 

 is 52 mm. long. Normal copulatory hooks are present upon the 



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