153 



conld find either the male frustules, or the scars left by them. With 

 regard, also, to Mr. Gilburt's remark, he did not wish to deny that if the 

 male frustules had not been present they would not have gone on dividing. 



Mr. Gilburt said it would of course be of great interest to see the passage 

 if possible, though he did not think that the mode of fertilization would be 

 disproved even if the passage was non-existent, because it should be re- 

 membered that in its earlier growth the band did not contain silex. 



Mr. Buffham said this was so, and the idea therefore was that the process 

 might be carried on through the sutures. 



Mr. Michael enquired how the exact form of the partition, as shown in 

 the model, was ascertained. The shape was very remarkable, and he 

 shonld like to know whether it could be seen, or if not, how it was found to 

 be so shaped ? 



Mr. Buffham said he had a slide under a microscope in the room which 

 contained a number of the frustules, some of which were attached, others 

 lying loose ; by careful focussing on the loose ones, it was quite possible to 

 see this shape. He might add that Professor Smith was quite in accord- 

 ance with him as to the observation. 



Mr. E. M. Nelson exhibited and described a rotating nose-piece, and also 

 a condenser. With regard to the former, he said he had frequently thought 

 that an object glass performed differently as an object was presented to it in 

 different azimuths. It had, however, occurred to him that this might be 

 due to the objective itself rather than to the altered position of the object 

 as regarded the light. Wishing, therefore, to test this, he had devised a 

 rotating nose-piece, by means of which, without shifting the object, the 

 objective could be turned upon its axis and used in different sectors. On 

 trying the effect of this with a glass which was believed to be of first- 

 rate quality, he found that whilst in one position it would resolve amphi- 

 pleura perfectly, it altogether failed to do so at another angle, showing 

 clearly that there was a difference in different azimuths. He thought this 

 might account for the fact that there seemed to be so much difference of 

 opinion as to the performance of certain objectives when used upon different 

 microscopes, and he suggested the desirability of being provided with a 

 simple contrivance such as he exhibited, in order to test objectives in all 

 azimuths, especially when about to purchase an expensive one — say at =£40. 

 He also exhibited a simple form of stage condenser, designed for small 

 cheap microscopes. It consisted of a meniscus lens, and a bi-convex lens, 

 put into a tube which was made to slide in another tube by means of a 

 spiral slit, so that it worked up and down quite smoothly in the same way 

 as a common pencil-case. The great increase in the amount of light was 

 remarkable. 



The President said there could be no question about the great improve- 

 ment in the light. The form of lenses was that of Herschell's doublet, 

 which he might say he had used himself for that purpose nearly 50 years 

 ago, long before achromatic condensers were thought of. He had had it 

 applied to his Chevallier microscope as a condenser, having felt the want of 

 more light — its efficiency for the purpose was so great that he should re- 

 commend it to everyone. 



