532 PROCEEDINGS OF THE SOCIETY. 



moved the stage in any degree, however slightly, which was not parallel, 

 the appearance of it would be materially altered. Anything which 

 interfered with the parallel position of the stage must bo destructive of 

 true definition. 



Mr. J. Mayall, jun., said he agreed very much with Mr. Beck in the 

 remarks which he had made ; but he thought if they took objection to 

 the movement upon the ground stated, they must take objection also to 

 the " Bausch and Lomb " fine-adjustment, where the body-tube was hung 

 on two parallel pieces of clock-spring, and which he assumed was a 

 movement in arc, although it did not alter the relation of the object to 

 the condenser. 



Mr. Beck said that the movement was a parallel movement and not 

 a tilting movement. The Bausch and Lomb arrangement was not the 

 same thing at all as the other, because the same parallelism was main- 

 tained, whereas in the tilting pattern they had the optical axis thrown 

 out of line perpendicular to the object. 



Mr. J. Mayall, jun., said that as he understood it, the Bausch and 

 Lomb movement compelled them to see a different portion of the surface 

 of the object with every change of the focal adjustment. 



Mr. Beck repeated that although this was so, parallelism was main- 

 tained. Some discussion took place as to whether the movement of the 

 tube was not in reality in arc ; but it was ultimately conceded that Mr. 

 Beck's view was correct. 



Dr. A. C. Stokes's paper on " New Infusoria Flagellata from American 

 Fresh Waters," containing descriptions of twenty new species, was read 

 by Prof. Bell ^ost). 



Messrs. H. W. Burrows, C. D. Sherborn, and G. Bailey's paper on 

 " The Foraminifera of the Bed Chalk " was also read by Prof. Bell (ante, 

 p. 383). 



Mr. Karop called attention to the recent investigations by Dr. W. 

 Pfeffer, on what he termed the " chemotaxic " movements of Bacteria, 

 Flagellata, and Volvocineaa, meaning by " chemotaxis " the phenomenon 

 exhibited by these organisms in the presence of certain substances which 

 attracted or dispersed them according to the nature of the stimulant 

 material. A given substance may act upon one organism, but not upon 

 another — e. g. dextrin excites Bacterium termo to an extraordinary degree, 

 but not Spirillum. 



Prof. Bell called attention to a paper recently published by Mr. 

 Wray, giving an account of the structure of a feather. 



The following Instruments, Objects. &c, were exhibited:— 

 Mr. Bailey : — Photomicroscope. 

 Mr. Bolton: — Mastigocerca elongata and M. rattus. 

 Mr. Crisp: — Dumaige's Portable Microscope, Objective Adapter, 

 and Camera Lucida. 



Mr. H. Mills : — Heteromeyenia radiospiculata n.sp. 



New Fellows: — The following were elected Ordinary Fellows: — 

 Messrs. William Cash, F.G.S., Henry C. Corke, Thomas W. Johnson, 

 M.D., and William Penman, Assoc. M.I.C.E. 



