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PHILOD1NA MACROSTYLA, EHR., AND ITS ALLIES. 



By James Murray. 

 (Communicated by D. J. Scow field, November 15t7i, 1907.) 



Plates 15 to 17. 

 Introduction. 



The following study has been undertaken mainly with the 

 object of summarising what is known of an interesting group 

 •of Bdelloids, and one which is puzzling to beginners on account 

 of the extreme variability of some of the species included in 

 it, and the fact that the known species are usually placed in 

 two different genera, whereby their relationship is obscured. 



The study is by no means exhaustive, as its completion on 

 a long ocean voyage prevented reference to some works in 

 which the species are mentioned, but it is hoped that all the 

 more important forms are noticed. All the forms which I 

 have been able to study in life are figured, as well as one 

 important variety which Mr. Rousselet has kindly permitted 

 me to draw from his excellent mounts. 



On the Genus Philodina. 



The genus Philodina was founded by Ehrenberg in 1830, 

 in the publication in which he made his first attempt at a 

 olassification of the Rotifera (6). 



His order Zygotrocha, including all Rotifers having the 

 ciliary wreath divided into two parts, contains an illoricated 

 family Philodinaea, which corresponds in the main with the 

 order Bdelloida, as now understood. 



The subdivision into genera is made to depend primarily on 

 the presence or absence of eye- spots and their position when 

 present, secondarily on the number of toes. The genus Philodina 

 is thus defined — " Oculis duobus, dorsalibus (pone organa 

 rotatoria), cauda ter furcata." In the genus as thus defined 

 he included three species — P. erythrojihthalma, P. aculeata, and 

 P. citrina. 



Journ. Q. M. C, Series II.— No. 62. 16 



