PLANARIA. 97 



The genus Planaria is susceptible, perhaps, of the subdivisions which 

 some naturalists propose to establish from the form of the body, the posi- 

 tion of the mouth, and the nature of the intestines. * These might be 

 useful, were it expedient to adopt the principles found to be practicably 

 applicable only in a few species. 



One obvious section may comprehend a Planaria with a flattened 

 body, specks or eyes on the upper surface, and an extensile proboscis 

 from the under surface. 



Another section might comprehend those with bodies not flattened, 

 and two or more distinct eyes on the front of the upper surface. 



But we are in fact scarcely prepared with materials sufficiently de- 

 finite for systematic arrangement, whence we must still submit to be oc- 

 cupied with rather a heterogeneous collection, selecting such specimens 

 for classification as expediency points out. 



1 . a. PLANARLA CORNUTA The Horned Planaria. Plate XIV. 

 Figs. 1, 2, 3, 4 ; Plate XV. 



This is the largest of the Scotish Planaria, one specimen having 

 occurred fifteen lines long, nearly half as much in breadth, a line thick, 

 and of a fine ruddy orange hue. But specimens only two-thirds of its 

 size, are the usual dimensions of full-grown adults. 



The Horned Planaria is of an oval shape, comparatively thin and flat, 

 the posterior part rounded, the anterior or head peaked, with two stout 

 obtuse horns, tending to a triangular form, rising from the back of the 

 neck. At the root of, and partly ascending each horn, are several black 

 specks, together with a few more somewhat behind them. Both sets vary 

 in numbers and distribution in different specimens, a remark applicable 

 to most of the soft-bodied animals, where specks are present. A milk- 

 white strong cartilaginous cylindrical proboscis, directed downwards, 



* Duges, Recherches sur les Planaries, ap. Annales des Sciences Naturalles, torn. xv. 

 p. 139 ; torn. xxi. p. 72. 



N 



