18 
THE VOYAGE OF H.M.S. CHALLENGER. 
all sides. A very small slit represents the opening between the two scuta. The 
antennae are the only extremities which still show their original condition ; the cirri 
have grown straight and functionless ; the parts of the mouth have disappeared. 
2. The cement apparatus is well developed as long as the male is young; when 
mature it is no longer so distinct. 
3. The intestine has become functionless and is quite rudimentary ; circulatory and 
respiratory organs may be passed by, as they have no distinct organs even in the herma- 
phrodite Scalpellum. 
4. The nervous system consists of a relatively small supra, oesophageal ganglion, of a 
not very stout oesophageal ring, and of a large thoracic ganglion. It is probably the 
latter which alone regulates the functions of the genital apparatus. The peripheral part 
of the nervous system is not much developed. The eyes (and other organs of sense) have 
been lost. 
5. The genital apparatus is the only well-developed system of organs. The female 
apparatus, however, is totally lost, and even the male organs show a great deal more 
concentration than do the same organs in ordinary hermaphrodite Cirripedia. In the 
first place the testis is single, and has become a rather compact gland, whereas in other 
Cirripedia it is double and scattered throughout almost the whole interior of the body. 
In the second place, the vesicula seminalis is also represented by a single vesicle only, 
hermaphrodite Cirripedia, on the contrary, having always two of them. 
Ln all these respects the little males of other deep-sea species of Scalpellum which I 
have been able to investigate exactly correspond to the male of Scalpellum regium. 
So does the male of Scalpellum vulgar e (from specimens from the Mediterranean) with 
the exception of the presence of rudimentary valves, which in that species, as in some of 
the deep-sea species ( vide p. 4), represent the so-called primordial valves of the young 
capitulum of pedunculated Cirripedia. 
c. General Observations. 
In the case of Scalpellum vulgare, Leach, Scalpellum rostratum, Darwin, Scalpellum 
peronii, Gray, sp., and Scalpellum villosum, Leach, sp., Darwin observed what he 
considered a penis ; in Scalpellum vulgare, Leach, and in Scalpellum villosum, Leach, 
sp., he ascertained, moreover, the presence of vesiculse seminales and testis in the 
specimens which were also furnished with ovaria. These specimens, therefore, were 
hermaphrodites, and as little males were found attached to their scuta, these male 
specimens got the very characteristic name of “ complemental ” males. On the other 
hand, Scalpellum ornatum, Gray, sp., did not show a trace of a proboscidiform penis 
in the four specimens which Darwin examined, and he, therefore, supposes that the 
animals studied by him were females, although it was impossible, as the specimens were 
