REPORT ON THE CIRRIPEDIA. 18 



dried, to demonstrate the absence of the vesieulse seminales and testes. The male animals 

 were lodged in a pouch on the under side of the scutum, in that case should not bear the 

 name of "complemental" males. From the state of the specimens of Scalpellum rutiliim, 

 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 most probable. 



Darwin's supposition as to the unisexuality of some species of Scalpellum, proves to 

 be in a very striking accordance Vv^ith 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 

 Scalj)ellum vulgare, Leach; I found the animal a truehermajDhrodite; it is furnished with 

 a well-developed penis, and the vesieulse 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 vesieulse seminales. 



The specimen of Scalp)ellum 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 

 lamella3. I got the same results when making a series of sections of ScalpelluTn 

 parallelogramma, Hoek (PL IV. fig. 9), and Scalpellum nympJiocola, Hoek (PL 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 smaU 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 tliere is still a third categorj' 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 halanoides, Hoek. In tlie d(>rii}itive 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 caro, 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 (PL IV. fig. 8, a.-f) ; I found that 

 the specimen was furnished with a very largely developed testis greatly surpassing the 

 Bame organ in Scalpellum vulgare. The penis of this specimen was also of considerable 



