EEPORT OX THE CIRRIPEDIA. 
19 
dried, to demonstrate the absence of the vesiculse semin ales and testes. The male animals 
were lodged in a pouch on the under side of the scutum, and in that case should not bear 
the name of “complemental” males. From the state of the specimens of Scalpellum 
rutilum, Darwin, which Darwin examined, it was quite impossible to ascertain whether 
the individual was a hermaphrodite or a female ; from the analogy of its nearest congener, 
Scalpellum ornatum, the latter, Darwin says, is the more probable. 
Darwin’s supposition as to the unisexuality of some species of Scalpellum proves to 
be in very striking accordance with the facts. What I at first considered to be the 
hermaphrodite form of Scalpellum regium (Wyv. Thoms.), Hoek, is not furnished with 
a penis, and does not show a trace either of a testis or a vesicula seminalis. To 
have full certainty in this respect, I divided the whole thoracic part of the body of a 
specimen of this species into a series of sections, and in none of them did even the smallest 
trace of a part of the male genital apparatus appear. The body was stained in toto by means 
of aluminium carminate, a most brilliant staining for the testis and for the sperma- 
tozoa within the vesicula seminalis when present. I then repeated the examination of 
Scalpellum vulgare, Leach ; I found the animal a true hermaphrodite ; it is furnished with 
a well-developed penis, and the vesiculse seminales have exactly the structure of these 
organs in species of the genus Lepas. The only difference is shown in their small size. 
Slightly more developed testes pour out their products into the vesiculse seminales. 
The specimen of Scalpellum regium , of which I examined a series of sections, was a 
full-grown animal ; it was furnished with males and there were ova in the ovigerous 
lamellae. I got the same results when making a series of sections of Scalpellum 
parallelogramma, Hoek (PI. IV. fig. 9), and Scalpellum nymphocola, Hoek (PI. IV. fig. 10). 
So I think that we may safely draw the following conclusions : — 
There are species of the genus Scalpellum , Leach, which show a very characteristic 
dimorphism. Some of these consist of large hermaphrodite and small rudimentary 
male specimens ; others have large female and small rudimentary male forms. 
However, I do not believe that these are the two most divergent cases in the sexual 
relations of the genus Scalpellum. I think there is still a third category of species in 
this genus, viz., those which are as true hermaphrodites as other Cirripedia, and in 
which no complemental males are developed. As a supposed species of this third 
division I will point out Scalpellum bcilanoides, Hoek. In the descriptive part of my 
report I have communicated the fact (p. 130) that one of the specimens contained eggs, 
though no complemental male was present at the place it ordinarily occupies. Though I 
have studied some more specimens of this species with great care, I have not once observed 
a male ; yet they were nearly all furnished with eggs. I then studied the body of one 
of the specimens by the aid of transverse sections (PI. IV. fig. 8, a-f) ; I found that 
the specimen was furnished with a very largely developed testis greatly surpassing the 
same organ in Scalpellum vulgare. The penis of this specimen was also of considerable 
