61 



ON A NEW CL(^SSlFICATION OF THE BDELLOID 



ROTIFERA. 



By David Bryce. 



{Ikai June 2Sth, 1910.) 



It has long been felt by tlioie who are interested in the Bdelloid 

 KoTiFERA that a revision of the classification of this groap would 

 considerably facilitate farther investigation into a comparatively 

 little-known corner of the animal kingdom. Daring the last 

 eighteen years the number of known species has more than 

 doubled, the great majority of the new forms being additions 

 to the two genera Fhilodina and Callidina, which have conse- 

 quently become overcrowded, unwieldy, and unsatisfactory. 

 Besides this, a more intimate acquaintance with the diversities 

 of structure and of habit of a greatly extended array of species 

 has proved that not only are the old generic definitions in- 

 adequate, but that they are also unreliable, and should no 

 longer be accepted. 



The object of this paper is to place the classification of the 

 Bdelloida on a more satisfactory basis, and it is hoped that the 

 arrangement now put forward will provide a sound foundation, 

 or. at the least, a new starting-point for future work, and that 

 the lines on which it is framed will prove to be reliable and true 

 to the natural relationships of the species with which it deals. 



From the point of view" of classification the Bdelloid Rotifera 

 have already experienced a somewhat complicated career. Their 

 history as a recognised group of allied species seems to have 

 begun in 1830, when Ehrenberg published his first Classified 

 .List of Micro-organisms (2), wherein he introduced the family 

 Zygotrocha, comprising all Rotifera with a ciliary wreath of 

 two similar parts. So far as regards the Bdelloida this earliest 

 classification may be summarised thus : 



Family Zygotrocha. 



Rotifera with corona of two similar parts (" ciliorum coronulis 

 binis ")j 



Loricate ..... Section Brachionaea. 

 lUoricate ..... Section rhilodinaea^ 



