THE SKIN. 



Girod has studied carefully the skin of Cephalopods, and this account is 

 little more than a confirmation for this species of his description. 



The epidermis is a simple epithelium which secretes a very thin striated 

 cuticle. It contains small clusters of, or more rarely isolated, cells in various stages 

 of mucous secretion. The shape of its cells varies according to the stresses to 

 which it is subjected. In the embryo and in a contracted state the cells are 

 cubical or columnar, while in the adult or when expanded they are slightly or 

 greatly flattened. The large nucleus lies near the center of the cell. A clearly 

 defined basement membrane is usually absent and irregular protoplasmic processes 

 interlock with the dermal cells. The epidermis which lines the siphon forms 

 two pairs of glands which were described by H. Muller in 185:3 as characteristic 

 Cephalopod organs. This description seems, as Brock has pointed out, to have 

 been overlooked by Verrill who described them more recently , by Hoyle 

 who named them collectively the "organ of Verrill", and by Laurie who 

 adopts Hoyle's name and who does not find them in the adult. The form of 

 these glands is described in connection with the siphon. The epithelium of the 

 glands is very highly columnar and contains vast numbers of goblet cells which 

 are contiguous or separated by very slender resting or recently emptied cells. 

 All the nuclei have a very unusual position at the distal ends and the secretion 

 gathers in the proximal ends of the cells, which seem inverted. The secretion 

 seems to consist of mucin and the glands seem to be active periodically, for at 

 times they are very conspicuous both in living and preserved animals, while 

 again they are inconspicuous. The glands are present in both sexes and at 

 all ages. 



Hoyle has described in the embryo of Sepia a trifid and in that of Loligo 

 a single line of modified epithelium. The tract in Loligo is longitudinal and lies 

 on the upper and dorsal surface of the mantle between the fins. It seems to 

 be a row instead of the usual cluster of mucous secreting cells. This has been 

 called Hoyle's organ. We have failed to find it, probably because the embryos 

 examined were too old. 



The epidermis also secretes the pen and the chitin-like rings of the suckers. 

 These will be described in connection with the skeleton and suckers. 



