146 



On the Adinetadj:, with Description of a New Species. 



By David Brtce. 



Plate XI. 



(Bead September 16th, 1892.) 



Among the numerous species of E-otifera which I find in 

 washings of various mosses gathered from different localities 

 and positions of growth, no one form is of such general 

 occurrence as Adineta vaga. It is not, however, one of those 

 species which; so far as we yet know, are only to be found in 

 what we may conveniently term moss-habitats, as it occasion- 

 ally occurs in pond-dippings, yet in my experience invariably 

 in limited numbers. But in moss-washings it is almost always 

 present, frequently abundant, and this fact suggests that this 

 species, like so many others of the Bdelloida, has special 

 structural and constitutional characters, which enable it to 

 flourish better amid the conditions of life obtaining in moss- 

 habitats than in the open waters of pools and ditches. 



As a Bdelloid, its most noticeable character is the form of 

 the ciliary organs. In place of the stout head and the 

 prominent pair of pedicelled discs bearing the ciliary wreaths, 

 or wheels, so conspicuous in the Philodinadae when swimming 

 or feeding, Adineta vaga has the ciliary wreath modified to a 

 mere furring of the ventral surface of a much-flattened head, a 

 furring which is exposed when the creature is travelling about, 

 by means of which it creeps, and which is not adapted for 

 swimming, but only for such creeping. If by chance dis- 

 lodged from any raised surface on which it is travelling, it 

 must fall through the water until arrested by the bottom or 

 some obstacle whereon it can again gain foothold. It must, 

 therefore, seek its food either on the bottom or on any surface 

 which it can reach without swimming. It is possible that this, 

 to some extent, may account for its supposed rarity, as the 



