VAEIATIONS IN THE SECONDARY SEXUAL 

 CHARACTERS OF THE FIDDLER CRAB 



PROFESSOR T. H. MORGAN 

 Columbia University 



In species in which the ordinary individuals are 

 sharply separated into males and females there are occa- 

 sionally found abnormal individuals in which character- 

 istics of one sex are mixed with those of the other sex. 

 We are only at the beginning of the study of these cases, 

 but enough work has been done to make it more than 

 probable that there are several, or even many different 

 kinds of situations that call for separate treatment. 

 That this is generally becoming recognized is evident 

 from the different names that have been used in describ- 

 ing these cases, such as intersexes, sex intergrades, her- 

 maphrodites, gynanders, androgynes, pseudo-hermaph- 

 rodites, free martins, eunuchoids, protandrous hermaph- 

 rodites; monoecious, dioecious, trioecious plants, indiffer- 

 ent larvae, neuter insects, etc. It seems to me not worth 

 while at present to attempt to classify such material until 

 we have learned more about it. Whether all or only some 

 of the aberrant types of fiddler crabs here described 

 should be called intersexes depends largely on the defini- 

 tion of what that term includes. 



In the fiddler crabs the male (Fig. 1 ^1) and the female 

 (Fig. 1 B) show not only the characteristic differences of 

 other decapods, but one of the claws of the male is 

 enormously enlarged. It may be either the right or the 

 left one. If removed a new claw of the same kind regen- 

 erates from the stump although it may take more than 

 one molt for the claw to become as large as the one re- 

 moved. In the fiddler "compensatory regulation" does 

 not take place as in some other decapods (Alpheus) ; 

 that is, after removal of the large claw, the smaller one 

 does not enlarge and substitute for it at the next molt. 

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