184 Heredity. 



are entirely gone, and the inside of the body is entirely 

 filled with a great testis, while the posterior end is pro- 

 longed into an enormous penis; and the animal hardly 

 deserves to be called an animal at all, as it is scarcely 

 more than an independent male reproductive organ at- 

 tached to the body of the female. 



This is certainly one of the most remarkable cases of 

 difference between the sexes, and no one who compares 

 Figs. 18 and 22 with Figs. 16, 17 and 19, can doubt that 



Fig. 21. Female of Alcippe lampas. Fig. 22. Male of the same species. 



among these barnacles the males differ from each other 

 much more than the females. 



'Among the higher Crustacea we find great numbers 

 of cases where the young male is like the adult female, 

 or the young of both sexes, but at maturity acquires 

 distinctive sexual characters. Any one who is familiar 

 with the Crustacea will acknowledge the existence of 

 this phenomenon, and it will only be necessary to 

 give a few illustrations. The adult male Lucifer is 

 distinguished from the adult female by the posses- 



