PROCEEDINGS OF THE SOCIETY. 489 



that the Council had been much gratified at the extremely cordial 

 manner in which the Societies previously nominated had received the 

 nominations. Two of them had done him the honour to elect him 

 an Honorary Fellow. 



Photographs (15) of blood, sent by Dr. J. B. Treadwell, of Boston, 

 U.S. (through Mr. C. Stodder), were shown, and the following letter 

 from Mr. Stodder read : — 



" Dr. Tread well's object is the measurement of the blood-disks and 

 comparison of size of human blood with that of other animals, and the 

 focussing is so done as to show the sharpest outline of the diameter. 

 I will call the especial attention of the Society to those photographs 

 on which there are two kinds of blood — blood from two animals. 

 Several devices have been used by others to accomplish this object, 

 one of much importance for obtaining in a picture the exact amplifica- 

 tion for both kinds of blood, and which, I believe, has not been S3 

 successfully before accomplished. I trust that these will be acceptable 

 to the Society. The mounting of the slides and the photographing is 

 all done by Dr. Treadwell." 



Mr. A. W. Waters' paper " On the occurrence of recent Hetero- 

 pora" (see p. 390), was read by Mr. Stewart, who also described by 

 drawings on the black-board the slide of Memhranipora membranacea 

 brought by Mr. Dreyfus. 



Mr. John Davis's paper on " A new species of Cothurnia ' 

 read by Mr. Stewart, and the drawings enlarged on the board. 



Mr. Wenham's " Note on Homogeneous Immersion Object- 

 Glasses " was read by Mr. Crisp (see p. 394) : — 



" From a paper contributed by me to the ' Monthly Microscopical 

 Journal,' June 1st, 1870, I quote the following comments in favour of 

 ' Homogeneous Immersion.' ' One advantage in the immersion 

 objective is that it almost prevents the loss of light from the reflection 

 of the upper surface of the cover and front of lens, and in part 

 neutralizes any error of figure and polish that may exist between 

 them. There is also another condition annexed, it has the singular 

 property of a front lens of adjustable thichiess, and therefore can be set 

 to the utmost nicety to balance the observations. Of course there is 

 no optical advantage attendant upon the use of imter. If a medium 

 of the same refractive power as the glass were to be employed, the 

 result woiild be better. Water having a low refractive index, an 

 adjustment is required for each thickness of cover, a'xl a difference of 

 adjustment is not so marked and sensitive as in the ordinary dry 

 objectives ; but if a medium of similar refraction to the glass were to 

 be used, no adjustment would be required for any thickness of cover, 

 supposing the test objects to be mounted thereon (which they generally 

 are), for in fact we should then view them all with a front of the same 



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