20 
THE VOYAGE OF H.M.S. CHALLENGER. 
size. Suppose I had observed this same organisation in a species 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 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,” 1 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 ” 1 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 capitulum and peduncle, with a mouth 
and stomach. 
Examples : — 
Scalpellum villosum, Leach, sp. j Scalpellum peronii, Gray, sp. 
(Scalpellum trispinosum, Hoek. 2 ) 
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. 3 ) 
1 Robin, Ch., Article “ Sexe ” in Dictionn. encycloped. cl. sci. med., Paris, 1880. 
2 The body of this species has not been investigated ; so my conclusion is based only on the presence of a well- 
developed penis, and on the great resemblance of the species 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. 
