^ THE VOYAGE OF H.M.S. CHALLENGEE. 



■aize. Suppose I had observed this same organisation in a spe,cies of another genus of 

 Cirripedia, then I should never have thought the existence of a complemental male in 

 that species possible, and now in the case of a species of Scalpelluon I think I may safely 

 infer that in this species the absence of a complemental male is not an accident, but indeed 

 the rule! I think, therefore, that there is sufficient reason to conclude thai the genus 

 Scalpellum presents the three following stages of sexual differentiation : — 



1st. True hermaphrodite species : all the specimens develop male genital products 

 as well as female. Whether these species are also " autogames," * i.e. whether 

 the spermatozoa of a specimen as a rule fertilize the ova of the same 

 specimen, is a point, which I do not wish to discuss at present. I will only 

 say that in case " autofecondation " ^ should be proved in the case of other 

 Cirripedia (which at present has not, I think, been done) we can also safely 

 admit it in the case of these species of Scalpellum. 



Example: — 



Scalpellum balanoides, Hoek. 



2nd. Large hermaphrodite specimens and small unisexual (male) ones in the 

 same species. 



A. Male specimens with a eapitulum and peduncle, with a mouth 



and stomach. 



Examples : — 



Scalpellum villosum, Leach, sp. | Scalpellum peronii, Gray, sp.. 



{Scalpellum trispinosum, Hoek.*) 



B. Male specimens with or without rudimentary valves, without, a 



peduncle, a mouth and stomach. 



Examples : — 



Scalpellum vulgare, Leach. | Scalpellum rostratum, Darwin, ■ 



{Scalpellum acutum, Hoek.^) 



> Bobin, Ch., Article "Sexe"m Dictionn. encyclop^d. d. sci. med., Paris, 1880. 



• The body of this species has not been investigated ; so my conclusion is based only on the presence of a weM- 

 deTeloped penis, and on the great resemblance of the species to Scalpellum villosum, Leach. 



* This species has not been investigated either ; the supposition as to its heimaphToditism is based only on the 

 presence of a well-developed penis.- ' ': 



