Our Fresh-Water Planarice. 445 



OCCULTATIONS. 



Jan. 6th. 48 Tauri, 6 mag. 9h. 20m. to lOh. 24m. 7 Tauri, 

 4 mag. llh. 28m. to 12h. 83m.— 30th. / Pisciuni, 6 mag. 

 9h. 56m. to lOli. 26m. 



OUR FRESH-WATER PLANARICE. 



BY W. HOUGHTON, M.A., F.L.S. 

 {With a Plate.) 



Anybody who has occasionally gathered water-cress, or searched 

 amongst aquatic weeds for objects for the aquarium, must be 

 acquainted with certain small black or brown creatures, of an 

 oblong form when at rest, soft, smooth, and flat, and about five 

 lines in length and one and a half broad. These are two species, 

 or, it may be, two varieties only, of Planarian worms. Probably 

 the collector of objects for the aquarium sees in these animated 

 black blotches very little to attract his attention, and he 

 throws them aside ; or if curiosity tempts him to bottle a 

 few specimens for examination, he finds that he is able to make 

 out very little of their structure, and sees scarcely anything to 

 interest him in their habits ; and certainly when we compare 

 these fresh- water Planarice with other rare and exquisite forms 

 of animal life, such a Cristatella, Freclericella or Plumatella 

 amongst our fresh-water Polyzoa, or a Melicerta or a Stephano- 

 ceros amongst the Rotatoria, these little black dabs have small 

 claims to beauty ; nevertheless the large white species, Pla- 

 naria lactea, with the pink arborescent ramifications of its 

 digestive system, is by no means devoid of beauty, whilst the 

 commoner black or brown kinds present many points of in- 

 terest to the naturalist, both in their habits and anatomy. 

 The Planarice, as their name imports, are of a flattened form ; 

 the under surface of some of the species bears some resem- 

 blance to the foot of a gastropodous mollusc. In many parts 

 of their organization the Planarice resemble the Flukes which 

 inhabit the liver and other viscera of various animals, especially 

 ruminants ; but none of the Planarice are internal parasites, nor 

 do they, like the Flukes, undergo a metamorphosis. They 

 inhabit fresh and salt water, and are to be found on the 

 leaves and stems of aquatic plants, and amongst the roots 

 of the Laminarice, between tide marks. On the present 

 occasion I shall confine my remarks to the fresh-water 

 species, of which a great number have been described as oc- 

 curring in France by Duges who has published two very 

 interesting memoirs on these animals.* In this country also, 

 * See " Annales des Sciences Naturelles," Tom. xv. and Tom. xxi. 



