REPORT ON THE CIRRIPEDIA. 29 



Targe series of sections of the peduncle of Lepas anatifera, the presence of the principal 

 cement-ducts can everywhere be ascertained ; in the most superior part of the peduncle 

 they run at a somewhat greater distance from the innermost layer of longitudinal muscle- 

 fibres than is the case in the more inferior sections of the peduncle. The ampullae which 

 would represent the commencements of the cement-ducts I have not observed. The two 

 ducts run in a zig-zag line, whence in many sections parts of them 0'3 mm. in length are 

 represented. I have not been able to follow the cement-ducts quite up to the inferior 

 extremity of the peduncle. The wall of the duct itself is irregularly folded in all my 

 preparations of Zepas anatifera ; towards the interior of the canal it seems to be invested 

 with a thin cuticle, for, when a transverse section is studied, its interior is always 

 limited by a sharp smooth line ; for the rest, I have not a very clear notion of 

 the cellular structure of the canal. The condition of the specimens of Conchoderma 

 virgatwm at my disposal has only allowed of my making a preparation of the glands. 

 They are very small, measuring not quite 0"06 mm. Their nuclei are nearly circular 

 and have a diameter of about 0'024 mm. In one of the glands a little nucleolus was 

 visible, though not very distinctly. The thin cuticle which invests the canal thafe-jiasses 

 away from the gland in Conchoderma virgatum was visible also round the glands them- 

 selves. I found Krohn's statement as to the occurrence of the cement-glands for the 

 main part in the parenchymatous tissue of the mantle to be quite correct. 



In Sccdpellum I studied the cement-apparatus in two species in greater detail ; viz. , in 

 Scalpellum vulgare, Leach, and in Scalpellum regium (Wyv.Thoms.), Hoek. In these 

 two species this apparatus is, curiously enough, not quite buildup after the same type. 

 That of Scalpellum vulgare has been described already )>y Darwin.' In young specimens, 

 Darwin says, the attachment is performed by cement-proceeding exclusively from the 

 antennae of the larva ; in older and full-grown specimens the cement is poured out 

 through a straight row of orifices along the rostral edge, thus causing a narrow margin 

 to adhere firmly to the thin and cylindrical branches of the coralline. "At each period 

 of growth the corium (the soft flesh, the mass of connective tissue with the muscles of 

 the peduncle) recedes a little from the attached portion of the peduncle ; of which portion 

 the greater part is thus left empty, &c. . . . The two cement-glands are -seated high u]> on 

 the sides of the peduncle ; the two cement-ducts proceeding from them, are ^^j-^ths of 

 an inch (0"039 mm.) in diameter and run in a zig-zag line ; at the point where they pase 

 through the corium to enter the lower attached jjortion of the peduncle they become 

 closely approximated, and partially imbedded in the membrane of the peduncle. Together 

 they run along the rostral edge, giving out through each orifice a little disk of brownish 

 cement, and finally they enter the larval antenna3." 



The specimen of Scalpellum vulgare, whose cement-apparatus I have investi- 

 gated, had a peduncle of about 9 mm. in length, and was attached by its under surface 



' Darwin, Lepadidse, 1851, p. 22G. 



