THE INTELLECTUAL OBSERVER. 



SEPTEMBER, 1865 



" SNAIL-LEECHES/' WITH A MONOGRAPH OF THE 



BRITISH SPECIES. 



BY THE EEV. W. HOUGHTON, M.A., E.L.S. 

 {With Two Plates.) 



Theee are many objects familiar to the eye of the aquarian 

 naturalist with which, however, he may be almost entirely 

 unacquainted, so far as relates to their habits and structure. 

 It is impossible to turn up a number of small stones in a brook, 

 or to examine many aquatic plants and submerged pieces of 

 wood, without discovering specimens of animal life, which, 

 perhaps, from their not very prepossessing appearance, we are 

 almost disposed to neglect. We are greatly delighted should 

 we meet with a piece of water-weed to which are attached 

 numerous Melicertce, and should our pocket-lens reveal the 

 presence of a few colonies of Stephanoceros, we are almost 

 wild with delight, but the writhing horse-leech and Nejphelis 

 we are inclined to look upon with no pleasurable feelings, and 

 should decidedly object to the introduction of such nasty, slimy 

 creatures to the other tenants of our aquarium. And yet the 

 graceful method in which many leeches swim is well worthy 

 our admiration, while the study of their anatomy will amply 

 repay any amount of patience bestowed upon it. The different 

 species of snail-leech, to which I am now introducing my 

 readers, do not generally present externally any very capti- 

 vating appearance, and yet they are objects of especial interest 

 to the naturalist, from the circumstance that some of this 

 family do literally deposit their eggs upon the underside of 

 stones and leaves, and sit upon them until they are hatched. 

 Again, from the great transparency of the young ones, it is, 

 comparatively speaking, an easy task to make out a good deal 

 of the structure and internal anatomy, while the facility with 

 VOL. VIII. — NO. II. g 



