D. BRYCE ON A NEW CLASSIFICATION OF THE BDELLOID ROTIFERA. 85 



4. Callidina socialis Kellicott is probably a good species, but 

 was quite inadequately described by its discoverer, who thought 

 it sufficient to differentiate his species from Philodina parasitica 

 as the only Bdelloid previously known to be ectoparasitic upon 

 fresh-water animals, and omitted in particular to ascertain whether 

 it was oviparous or viviparous, and whether it had three or 

 four toes. Janson, who considered that Rotifer magnicalcarata 

 (Parsons) is identical with C. socialis, assumed that the latter 

 was viviparous and had three toes like Parsons's species. In my 

 view it is quite as likely to have been oviparous and four-toed 

 like P. commensalis Western (described as viviparous, but I think 

 in error). There are now known quite a number of these ectopara- 

 sitic species, and any amended description of the true C. socialis 

 would have to take these into consideration. Meanwhile I retain 

 as valid the E. magnicalcarata (Parsons), which I have repeatedly 

 found and which is a much larger form than that described by 

 -Janson, attaining sometimes a length of 720 fx or ^V inch. 

 Janson 's dimensions and details apply very well to another 

 smaller form, found by Murray in Scotland and myself in 

 England, which has the same sword-like spurs as P. commensalis 

 iind R. magnicalcarata, and like these species is usually found on 

 Asellus. This third form resembles P. commensalis very closely 

 in general appearance, but is viviparous, three-toed, and blind. 

 In P. commensalis the eyes are frequently very difficult to define, 

 and I am inclined to believe that Western took the character 

 " viviparous " from examples of this third form which he had 

 failed to distinguish from the true commensalis. 



5. Philodina hexodonta Bergendal. A form found some years 

 ago in Scotland by Murray, and more recently by myself, was 

 at first referred to the above species, in view of the approxi- 

 mation of the number of teeth (5 5) to that stated by Bergendal. 

 It differs from it, however, in almost every other detail given 

 by that writer. For instance, P. hexodonta is said to have a 

 body resembling that of P. roseola, but not reddish ; and to 

 have spurs so swollen at the base that there is no interstice 

 between them. The Scottish form is quite unlike P. roseola in 

 general outline; the proportionate length of the foot is very 

 different, the body is often reddish, and there is a distinct 

 interspace between the short, acute spurs. 



After further consideration I came to the conclusion that 



