452 Our Fresh-Water Planarice. 



Planar ice soon die when taken out of the water, a drop 

 of spirits of wine or other alcohol, kills them instantaneously 

 and renders their bodies hard ; vinegar softens but does not 

 dissolve them. 



The Planarice belongs to the order Turbellaria, whose 

 characters are thus given by Dr. Johnston : " Worms individual, 

 locomotive, very rarely tubicolous, monoecious, or dioecious, 

 with or without eyes, the surface usually coloured, and 

 sometimes in elegant patterns, transparent or opaque. Body 

 soft, parenchymatous or cavernous, fiat or sub-cylindrical, 

 naked and lubricous, covered more or less with vibratile cilia, 

 and sometimes with papillse, often very contractile, and 

 polymorphous, and sometimes breaking up voluntarily into 

 pieces, head continuing "with the body, or rarely, imperfectly 

 defined, either without tentacula, or with two frontal or dorsal 

 ones prolonged from the surface. Mouth either terminal or ven- 

 tral, and in the latter case situated in the anterior third, or near 

 the centre, or towards the tail; often furnished, with a 

 prehensile proboscis. Intestine dendritically branched, or 

 undivided, with or without an anus, Zoophagous, but some 

 appear to feed, occasionally at least, on decaying plants. 

 Oviparous, or viviparous, very rarely multiplying by spon- 

 taneous division. There are no suckers or discs, and 

 progression is made by gliding or by natation. They are never 

 internal parasites, but tenant fresh and salt water, and are 

 found sometimes in moist places. The skin is very rarely 

 iridescent, and there is no phosphorescent species." 



As Dr. Johnston's book* is probably in the hands of only a 

 few readers it may be well to give here his classification of the 

 British genera. The order Turbellaria he divides into two 

 sub-orders, viz . I. Planariea and II. Teretularia. The first 

 order alone concerns us at present ; it is thus defined : — 



" The body, parenchymatous, flat, or flattened, usually onl}- 



a little longer than broad, acephalous, with or without eyes 



on the dorsum in front. Mouth, a simple pore, often the 



aperture to a prehensile proboscis. Anus, none. Genital 



pore, posterior to the oval.'" This sub-order, Planariea, 



is divided into three families, with their respective genera, as 



follows : — 



negatived that idea. Whether the fresh-water Dendrocoels or Rhabdocaels ever 

 go through a larval condition I know not. I have hatched scores, and always 

 noticed that the young exactly resembled their parents. 



* I am well aware that Dr. Johnston's catalogue of British non-parasitic 

 worms is far from complete ; nevertheless, as it is the only English text book on 

 the subject, and the work of a very accomplished naturalist, I have preferred in 

 this paper to retain it. It must be confessed that at present the subject of the 

 Planarian worms and other Turbellaria is involved in obscurity. Identification of 

 species is difficult. Young specimen have, it is probable, been sometimes taken 

 as distinct species. 



