30 THE VOYAGE OF H.M.S. CHALLENGEE. 



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 m 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 Scali^ellum vidgare in alcohol, the glands appear as little white grains and are visible 

 even with the naked eye. Often the glands are not tmicellular 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 (PL V. fig. 6*) ; the size of the 

 gland was O'll to 0"125 mm. in diameter, that of the nucleus 0"04, whereas the nucleolus 

 measured O'OIS mm. Theducts at the end of which the glands are observed are verynarrow, 

 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. 



AU 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, 

 Scalpelhim) 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 

 chitiuous wall — perhaps the chemical composition is difi"erent 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 (PL 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. 



