64 
are influenced by it, as is clearly visible on the sections through 
difFerent parts of the body. 
Of special interest is that there is a transformed outer layer 
in each of these supporting cells. The substance forming it, 
a metaplasmatic product, is, even at the strengest magnification, 
homogeneous and it imbibes easily with staining agents. With iron 
hematoxylin it attains an appearance similar to that of a cuticle. 
Such a layer, extremely rare in the Polyclads, is described for a 
great many other Turbellarians (f. i. Alloeocoeles) and has verbally 
been called a cuticle, a name which I shall not adopt, as I find 
it not adequate. At a cellular height of 15 — 20 and a breadth 
of 6 this metaplasmatic layer is little more than 2 thick. 
Outside of it are basal corpuscles of the cilia and through it 
the „Cilienwurzeln“ pass and continue further downwards through 
the protoplasma of the cell. 
Most of the epidermal giand cells produce rhabdites. The cyano* 
phile secretion is formed in the subdermal giands and their ductuli 
pierce the body-wall of the ventral side. 
Another feature of yet greater importance for the knowledge 
of the epidermis of the Polyclads is the occurrence of a kind of 
adhesive cells. There was, of course, no possibility to study 
them in the type specimen from Galapagos from the middle of 
the 19th century. These cells distinguish themselves very clearly 
from all other epithelial cells both in cytological structure and in 
location. They are strictly limited to the submarginal zone and 
there they form a nearly circumferential band leaving the anterior 
end more or less free. The band is broadest at the posterior 
end, but at the sides of the body reaches at least 500 (.i in 
breadth. No ordinarily ciliated supporting cells occur in these 
submarginal zones and no ordinary giand cells. The secretion, 
rhabdites, acido- and cyanophile secretion is received from giand 
cells in the parenchyma. 
Lang has especially looked for adhesive cells in Polyclads, but 
with negative result in respect to fullgrown animals. He says thus 
(1884, pag. 57): „Auch auf Schnitten håbe ich nie Elemente im 
Epithel angetroffen, die ich hatte auf Klebzellen beziehen kdnnen; 
ich weiss iibrigens von der Untersuchung von Gunda segmentata*) 
*) Identical with Procerodes lobata. 
