392 History of the Hairy -backed Animalcules. 



relation of the family in question. Assigning to them a pro- 

 visional place among the Turbellaria, as just indicated, he 

 admits that further investigations of the anatomy of this little 

 examined group may bring to light relations hardly suspected ; 

 while many forms more or less closely allied may still lurk un- 

 discovered, acquaintance with which may modify our already 

 accepted conclusions. Dujardnr's curious little Ecliin-odera, and 

 my own equally anomalous Taphrocampa, appear, for example, 

 to widen the distance between the group and the Turbellaria ; 

 while, in their more strongly marked segmentation they show 

 a decided approach to the Annelidous forms. 



Having thus given to the reader an abstract of the views of 

 one of the most learned of Continental zoologists on this obscure 

 group, I proceed to describe all the species as yet recognized 

 in it, premising that I have myself met with some, manifestly 

 belonging to before-unknown genera, and other species which 

 seem irreconcileable with published descriptions and figures of 

 such as had been recognized. These I propose to include. 



FAMILY CH^TCMOTIDiE. 



I think it desirable that the family should be named after the 

 most characteristic and most populous genus, which is indubit- 

 ably Chcetonotus, and not Ichthydinm. It consists of soft- 

 bodied animals microscopically minute, of lengthened form, 

 having a bilateral symmetry, with a more or less distinct 

 separation of the head; the body more or less clothed with 

 vibratory cilia, and for the most part with long hairs ; the 

 alimentary canal straight, and furnished with an orifice at each 

 extremity. Inhabitants of fresh-water. 



Genus I. — Ichthydium (Ehrenberg) . 



Posterior extremity forked ; body unfurnished with hair. 



Sp. 1. I. podura (Mull.) This form has been often seen 

 by the curly observers, if we can be quite sure that it has not 

 I Men confounded with Olicet. lams. Ehrenberg first certainly 

 defined it, having met with it in Nubia, among conferva from 

 the Nfle, and subsequently near Berlin. The body is linear- 

 oblong, with iIk 1 anterior extremity swollen; sometimes three- 

 lobedj often slightly eonstrictod; the hind fork short. The 

 ventral Burfaoe is fiat, the dorsal arched, and destitute of hair. 

 The largest specimens hare not the least vestige of hair on the 

 back. The animal is colourless or whitish, but sometimes 

 tinged with yellow, through (lie distension of the wide intes- 

 tine. A longitudinal band of cilia was in one specimen clearly 

 seen by Ehrenberg, along tho belly, but in other individuals, 



