30 
THE YOYAGE OF H.M.S. CHALLENGEB. 
to the rather broad stem of a horny coral. In order to be able to make transverse 
sections of the peduncle, I have removed the chitinous wall of the peduncle with its 
calcareous scales. I stained the peduncle in toto by means of aluminium carminate. 
The ovary in this specimen was very strongly developed, and its coeca extended as far 
as the most inferior part of the peduncle. The true cement-glands have nearly the same 
shape and structure as in the other genera ; in size they are larger than those of Concho- 
derma, but not so large as those of Lepas. They are rather numerous in the superior part 
of the peduncle, but become scarce lower down (PI. V. fig. 6). On opening a peduncle 
of Scalpellum vulgare in alcohol, the glands appear as little white grains, and are visible 
even with the naked eye. Often the glands are not unicellular but composed of two or 
three cells combined ; in that case the body of, the gland is larger, and the two or three 
nuclei of the original cells are distinctly visible. In many of the glands a dark coloured 
oval nucleolus was present within the circular nucleus (PI. V. fig. 6 # ) ; the size of the 
gland was Oil to 0125 mm. in diameter, that of the nucleus 0'04, whereas the nucleolus 
measured O'Ol 3 mm. The ducts at the end of which the glands are observed are very narrow, 
their diameter being about 0'007 mm. ; those of adjoining glands often anastomose, so as 
to form together a network of ducts. I know these anastomosing canals from a prepara- 
tion stained with picrocarmine and isolated by the aid of needles. In the transverse sec- 
tions of the peduncle only very small parts of the ducts are seen attached to the glands. 
All the narrow ducts pour their contents into four rather wide canals which, at the 
rostral side, run longitudinally through the peduncle. Immediately below the place in 
the superior part of the peduncle, where the two oviducts terminate, the first longitudinal 
cement-duct begins (PI. V. fig. 6, d). It is closed at its superior extremity, the cement 
being shed in the canal by means of lateral openings. The blind extremity of the canal 
is placed a little more towards the centre of the peduncle ; the canal slightly changes its 
direction so as to run parallel with and close to the elongated cavity (fig. 6, a), which 
is visible at the rostral side of most pedunculated Cirripedia {Lepas, Conchoderma, 
Scalpellum), and which is a continuation of a part of the body-cavity of the animal within 
the capitulum. The width of the cement-duct is about 0‘3 mm. It is surrounded by a 
chitinous wall — perhaps the chemical composition is different from that of chitin — and 
it shows traces of an epithelial (or rather endothelial) cell-layer on the internal surface. 
About half-way along the peduncle a second longitudinal canal begins ; it has, when seen in 
transverse section, a long oval shape, and is divided by a partition into two halves, which 
soon become independent. A little lower a third — properly speaking a fourth — canal 
begins (PI. V. fig. 7). It has an oval shape; its largest diameter is 0 - 4 mm., its shortest 
0’28 ; its wall is composed of a chitinous (?) outer layer and a regularly developed inner 
epithelial layer of very small cells with distinctly coloured nuclei. I do not quite under- 
stand why this epithelial cell-layer is well developed (at least distinctly visible) in the one 
duct, whereas it can scarcely be made out in the other ducts. 
