expect to find in this genus also that the epidermis over the ten- 
tacular eye-groups will indicate the location of tentacular rudiments 
through the absence of giand cells. 
Bo dy-Wall: The epidermis contains, especially on the dorsal 
side, a great mass of giand cells producing a granular, eosinophilous 
secretion. The rhabdit-cells, on the other hånd, are neither ventrally 
nor dorsally present in excessive numbers, as is also the case with 
the basophilous giand cells. The frontal sense furrow is extremely 
near the anterior margin of the body, lying just subterminally. In 
association with this organ there are, besides the usual subepithelial, 
basophilous giand cells, some eosinophilous ohes occurring together 
with the former. 
For a number of Polyclads I have had an opportunity to describe 
a special kind of giand cells occurring in a submarginal zone around 
the body, in the epithelium, or in the peripheral parts of the body- 
parenchyma. Such giands do not occur in Leptostylochus. 
The basement membrane is moderately thick and looks quite 
homogeneous. The muscle wall of the body is remarkably thin and 
does not exceed the epidermis in stoutness. This is at least true 
with regard to the dorsal side, and the middle and peripheral zone 
on the ventral side. It is perhaps superfluous to mention that the 
ventral epidermis does not attain the thickness of the dorsal, being 
about Vs the height of the latter. It is of special interest that the 
outer „transversal" muscle layer is so well pronounced that it 
stands out distinctly even on using a low magnification. The feeble 
development of this layer, usually consisting of only a single row 
of extremely fine transverse fibres below the basement membrane, 
has caused the earlier authors on Polyclads to overlook it. In 
Leptostylochus the fibres, at least most of them, meet each other 
in an acute angle, thus forming two diagonal layers, each two or three 
fibres thick. In other respects the normal appearance of the muscle 
layers occurs, but for the faet that the layers are remarkably thin. 
On the other hånd, it is very noticeable that the dorso-ventral 
fibres are present in excessive number, being densely arranged in 
groups. The individual fibres are also very coarse. 
Alimentary system: The mouth lies approximately at the 
beginning of the last fifth of the pharyngeal pocket. The pharynx 
is extremely richly folded and filis up the pharyngeal pocket rather 
