204 THE ZOOLOGIST. 



the slide ; it was only occasionally extended horizontally so as 

 to project a little way beyond the edge of the lorica. 



3. Pterodina valvata, Hudson. — Among a large number of 

 Pterodinas obtained from Langleybury Pool on May 12th, 1913, 

 were some which, being but slightly stippled, were remarkably 

 transparent. These presented about a dozen comparatively 

 large bosses, which were well-defined and nearly equidistant. 

 As they glided slowly across the field, these Pterodinas were 

 beautiful objects. Fig. 1 represents one of them, its foot being 

 drawn in order to show its peculiar form, although this parti- 

 cular specimen rarely extended its foot beyond the lorica, when 

 exposing its dorsal part to view. After gliding about for some 

 time, it attached itself by its foot to a piece of Conferva and then 

 remained stationary or nearly so for a long time. 



I did not see one of the specimens of P. valvata fold its lorica, 

 although I watched for a time in expectation of seeing this 

 phenomenon, from the occurrence of which the specific name of 

 the Rotifer was derived. It seems, however, that P. valvata 

 rarely folds its lorica, for Mr. P. H. Gosse says : " As a rule, the 

 folding of the valves is somewhat rarely performed. I have 

 observed probably hundreds at various times, and I think I have 

 not seen half-a-dozen folded " (' TheRotifera,' &c, C. T. Hudson 

 and P. H. Gosse, vol. ii. 1886, p. 113). 



4. Brachionus rubens, Ehren. — A vast number of specimens 

 of this beautiful and active Rotifer were obtained on October 3rd, 

 1913, from a small, shallow pool at the eastern side of Potten 

 End, and close to the road from that place to Water End. The 

 water of this pool was quite green with Conferva and minute 

 aquatic plants. Many specimens were also obtained on October 

 15th, 1913, from Wigginton Pool. The water of this pool also 

 was of a green colour, as seen in the collecting bottles, but not 

 nearly as green as the water of the Potten End Pool, there being 

 only a comparatively small quantity of Conferva and minute 

 aquatic plants in the Wigginton Pool. This difference in the 

 nature of the waters of the two pools probably accounted to an 

 important extent for the great difference in numbers of B. rubens 

 in the two pools. The waters of Potten End Pool had every 

 appearance of a rich feeding medium. 



Many specimens of B. rubens were seen swimming freely in 



