388 History of the Hairy -backed Animalcules. 



seen sidewise, reminds one of that of a ferret, the back being 

 much arched (Plate i. Fig. 1) . The whole body appears covered 

 with hairs, which are set in rows ; those on the front part are 

 smaller and closer, those on the back larger and fewer. The 

 fore-part, seen from beneath, presents an appearance of hatch- 

 ing or cross lines running diagonally, or else of dots set in 

 quincunx, which I suppose are the bases of the hairs growing 

 in such an arrangement. The internal structure is not usually 

 discernible ; for though the body is pellucid and colourless, and 

 often lustrous from the refraction of the light, especially 

 through the neck, the number of hairs which stud the surface 

 prevent a clear sight of the interior. Two bands, which run 

 down the belly, are understood to be bands of cilia. There is 

 a certain nimbleness and sprightliness in the motions of this 

 pretty animal as it crawls, frequently turning short on itself and 

 changing its course (see Fig. 2), examining various objects, 

 much like a caterpillar does, with apparent intelligence. I shall 

 return to this species again for fuller details ; but this general 

 description will help the reader better to understand the group 

 of which I propose to treat. 



The form appears to have been recognized in the earliest re- 

 cords of microscopic observation; for Joblot, nearlya century and 

 a half ago, described an animalcule, which was probably enough 

 this very creature, under the title of (t Poisson a tete tivhYe." 

 I say " probably," because an approximation to the general 

 outline of such minute creatures was all that, with their very 

 imperfect instruments, the early observers could accomplish. 

 About sixty years later Miiller, the great Danish zoologist, and 

 the first who attempted to define and arrange the host of micro- 

 scopic animalcules that were crowding upon observers, de- 

 scribed under two names — O&rcaria podwra and Trichoda larus 

 — what may have been two species of the same family, or one. 

 The two specific names have, however, been adopted in modern 

 nomenclature, as representing two distinct creatureSj the latter 

 being appropriated to flic one I havo described ; though on 

 wh;it account he applied the name laru8 } which signifies << gull, 



to it, I cannot conjecture. Passing by other observers, who 

 h;ivc recorded nothing more worthy of note concerning the 



form, tbaD that they recognized it, we come to Ehrenberg, who, 



in hi:- valuable papers in the Transactions of the Berlin Academy 



lor L 831, and afterwards in his notable work Die Infusions* 

 thierchen, determined the two genera, Ichtkydiim and Ohceto* 

 nofois, for the two species described by JV1 idler, adopting his 

 Specific names, and added two more species to the latter 



HIS. 



The great Prussian zoologist iu eluded these creatures among 

 the RoTIPBEAj uniting with them in the same group two other 



