162 PROCEEDINGS OF THE SOCIETY. 



Mr. H. Jackson's note was read, recommending monobromide of 

 naphthaline as a medium for homogeneous immersion {swpra, p. 119). 



The President said that the Society would regret to hear of the 

 death of Dr. Zeiss, of Jena, which had taken place since the date of 

 their last meeting. He had lived to the good old age of seventy-three 

 years, and was known to many amongst them, though not to himself. 

 But he knew a great deal about his lenses, because it had come to this, 

 that practically he had been obliged to put aside all large-angled English 

 lenses in favour of those of Zeiss's manufacture. For delicate and flat 

 work nothing could be better than the lenses produced by our best 

 English makers ; but when they had to deal with an active animal not 

 more than 1/250 in. in length, it was of immense advantage to get that 

 additional focal distance which these foreign lenses afforded. Then 

 another thing in which Dr. Zeiss had departed from the English plan 

 was in not attempting to make screw collars to his high-power objec- 

 tives, but fixed the combination once for all at a given thickness which 

 his experience found to be the best average working distance. The 

 benefit of this was found at once when a delicate animal of about 

 1/300 in. was being held in such a way that the slightest pressure would 

 crush it, and perhaps it was also the only one of its kind yet seen. At 

 such a time it was best to have a lens that was fixed, and did not require 

 a troublesome adjustment to be made at the time. Then he found also a 

 further advantage in the fact that this kind of lens admitted of the use of 

 dark-field illumination to a greater extent than our own. Even with 

 the very highest powers some kind of dark field could be obtained, and 

 would show what could not otherwise be made out so well. Some people 

 said that this was only a matter of display ; but this was not all, for 

 with many of the Kotifera it was necessary to use this method of 

 illumination in order to obtain a true idea of their structure. 



Mr. Crisp said he must add some tribute to the memory of Dr. Zeiss, 

 on account of the great courtesy he had always extended to them as a 

 Society. There was nothing they had ever asked for but they had got 

 it immediately. 



Mr. J. Mayall, jun., said he should like to add his testimony also as 

 to the value of the services rendered to microscopy by the late Dr. Zeiss. 

 When he was at Jena some time ago, in discussing with Prof. Abbe the 

 progress that had been made in the Microscope since the introduction of 

 achromatic objectives, his attention was called to the fact that Dr. Zeiss 

 had devoted himself specially in his early days to perfecting the simple 

 or dissecting Microscope, and that he had succeeded in obtaining such 

 large apertures with his doublets and triplets that, in resolving power, 

 they were nearly on a par with the best contemporaneous German 

 compound Microscopes. Prof. Abbe thought the technical skill shown 

 by Dr. Zeiss in the production of these doublets and triplets had led 

 him to neglect for many years the compound Microscope, and hence, 

 probably, to retard the development of the compound Microscope in 

 Germany. Simple Microscopes had been much more in vogue on the 

 Continent than in England until about thirty years ago, and the favour 

 they had met with was largely due, without doubt, to the enormous 

 apertures obtained by certain skilled opticians, notably the late Dr. 

 Zeiss. 



