134 



one species only. The Adinetidae include two genera which 

 differ very notably in the structure of the foot. The Philodinidae 

 are represented by thirteen genera, including at least nine-tenths 

 of the Bdelloida known at this time. To reduce this unwieldy 

 crowd of species into order it has been necessary to bring into 

 use details hitherto unemployed for generic distinction. With 

 few exceptions, the great majority of the species conform very 

 closely to one structural plan. One particular deviation from 

 uniformity has been considered of high importance. It is found 

 that the proportion of the lumen, or inner cavity of the stomach, 

 varies from the normal type in certain species which are other- 

 wise closely related, and which have the common characteristic 

 (but characteristic of them only) of moulding the food into pellets. 

 In these species the lumen of the stomach is nearly as great as 

 the whole diameter of the organ, whereas in the normal type of 

 stomach the lumen is relatively narrow. The Philodinidae are 

 thus separated into two sections, with wide and narrow lumen 

 respectively. In the author's opinion, the species with the wide 

 lumen, about one-fourth of the family, represent an earlier stage 

 in the evolution of the family type than that indicated by 

 the species with a narrow lumen. In this section are three 

 genera. 



The species which have the lumen narrow divide naturally into 

 three sub-sections: (1) with four toes; (2) with three toes; (3) 

 with toes bearing a number of cup-like suckers, or united to form 

 a broad disc or twin discs. The four-toed species are considered 

 to be the most highly developed of the Bdelloida, and are divided 

 into five genera, including the veteran genus Philodina under 

 amended definition. The species with tiiree toes are represented 

 by two old genera. Rotifer and Callidina, also under amended 

 definitions. The third sub-section contains species relatively 

 few in number, but mostly of large size, which have been dis- 

 tributed among three genera. 



The chairman, Mr. C. F. llousselet, said that the Bdelloid 

 rotifers were quite a specialist's study. He had found them so 

 intricate that he now left them alone. Mr. Bryce had made a 

 special study of this particular group, and there was no one 

 better able to revise the classification than he. 



Mr. James Murray said that Mr. Bryce's paper was possibly 

 of greater interest to him (Mr. Murray) than to any one else in 



