20 THE VOYAGE OF H.M.S. CHALLENGER. 



size. Suppose 1 had observed this Bame organisation in a species of another genus of 

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

 that species possible, and now in the case of a species of Scalpellum 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 that 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 " J 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, Iloek. 



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

 same species. 



A. Male specimens with a capitulum 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. Scalpd/um rostratum, Darwin. 



[Scalpellum acutum, Hoek. :! ) 



1 Robin, Cb., Article "Sexe"in Dictionn. encyclopecl. d. bci. med., Paris, 1880. 



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

 developed ] enis, and on the great resemblance of the apeciea to Scalpellum villosum, Leach. 



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

 presence of a well-developed penis. 



