182 Heredity. 



fied, while Fig. 18 is of nearly the natural size; but 

 with this exception the complementary male is essen- 

 tially like the hermaphrodite, and it has the structure 

 of an ordinary stalked barnacle. There is a distinct 

 peduncle, which carries a triangular capitulum, and 

 although the plates are somewhat reduced in number 

 they agree in form and position with the chief plates of 

 such a species as Pollicipes. The animal inside the ca- 

 pitulum is much like an ordinary barnacle, the essential 

 difference being the total absence of female reproductive 

 organs. It is a male and nothing more. 



FIG. 17. An hermaphrodite barna- FIG. 18. Complemental male of the 

 cle, Scalpellum villosum. same species. 



Figure 19 shows the female of another species, Ibla 

 Cummingi, which does not differ essentially from the 

 forms shown in Figs. 16 and 17, but the female of 

 Ibla Cummingi is a true female instead of an hermaph- 

 rodite, and there are no traces of male reproductive 

 organs, but inside her shell, and planted by a long root- 

 like process, there is a minute parasitic male, shown] in 

 Fig. 20, magnified thirty-two times, while the figure of 

 the female is magnified only five times. In Fig. 20, 

 b is part of the wall of the body of the female, and 

 a is the long root by which the parasitic male is planted. 



