PLANARIA. 125 
three miles east of it, with very few of the panniculata among them. 
The largest and finest black Planarize are in Duddingston Loch, at the 
base of Arthur's Seat, but in the preceding two places they are compara- 
tively rare and small. Nor have I observed either the /actea or pannicu- 
lata along with them. 
On the whole, I view all that is said only as so many materials in 
aid of the construction of some system on a solid basis. 
But from these and other observations, it may be deduced that,— 
I. The genus Planaria is common to the seas and the fresh-waters 
of Scotland ; but the proportional numbers in the former much smaller 
than in the latter. ; 
II. That the genus is distinguished by groups of considerable diver- 
sity of shape, some being thin and flattened individuals ; others almost 
cylindrical, and some approaching a conical or double conical form. 
III. That their distinction is also seen in indefinite external organs, 
such as subtentacula or cornicula, and the appearance of specks more or 
less numerous, or of what resembles eyes, while in many none such can 
be discovered. 
IV. Some are distinguished by the form and position of the mouth, 
being an aperture in front, a slit in the under surface, near the anterior 
margin, or a proboscis far behind, protruding from the under surface. 
V. The food, for the most part consisting of animal substances, is re- 
received into an ovoidal stomach, and in some is distributed in numerous 
pinnate interanea, extending nearly to the margin of the animal. Pla- 
nariz are in general carnivorous ; some seem to consume the succulent 
parts of vegetables. 
VI. Planariz feed greedily, and some to such excess as to burst the 
integuments. They are proportionally capable of long abstinence, which 
diminishes their size, and impairs their colour. 
VII. Planariz are of different sexes, or they are androgynous. They 
propagate by ova, containing one or several embryos. 
VIII. Certain young Planarix apparently undergo metamorphosis 
in advancing to maturity. 
