PLANARIA. 12-3 



three miles east of it, with very few of the pannicidata among them. 

 The largest and finest black Planarise 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 lactca 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- 

 nariae are in general carnivorous ; some seem to consume the succulent 

 parts of vegetables. 



VI. Planariae 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. PlanariaB are of different sexes, or they are androgynous. They 

 propagate by ova, containing one or several embryos. 



VIII. Certain young Planarias apparently undergo metamorphosis 

 in advancing to maturity. 



