220 PROCEEDINGS OF THE SOCIETY. 



as to the nature of the white i)owclcr meutioned as being found upon 

 one species of the mites ? 



Mr. Michael said that he had little doubt as to the use of this 

 powder, which seemed clearly to be of a jn-otective character. Many 

 other species not provided with powder, made a similar protection for 

 themselves by rolling in the mud. As to its origin, he was unable to 

 say anything with certainty, but thought that the cast skins had some- 

 thing to do with it. 



The thanks of the meeting were given to Mr. Michael for his 

 paper. 



Dr. George Hoggan read parts of a paper " On the Development 

 and Retrogression of Fat-Cells," in which the results of a series of 

 observations and experiments carried out by himself and Mrs. Hoggan 

 were minutely detailed. The subject was well illustrated by prepa- 

 rations exhibited under twelve Microscoj^es in the room. 



The President, in proposing a vote of thanks (which was carried 

 unanimously) for Dr. Hoggan's very interesting communication, said 

 that so many paints of interest had been referred to that a great 

 deal of time would be needed to discuss it thoroughly. 



Mr. Beck placed upon the table and described in detail a new large 

 binocular Microscope which he had devised with swinging bar for 

 condenser, mirror, and lamp, and with improved movements, and 

 invited the Fellows to criticise it freely at the close of the meeting, 

 with a view to its possible further improvement. 



Mr. Crisp, in calling attention to the new y^g^ oil-immersion objec- 

 tive of 1-26 numerical aperture (or the large balsam angle of 114° 18')", 

 said that they had a very interesting communication from Professor 

 Abbe on oil-immersion objectives in general, which there was unfortu- 

 nately no time to read, but of which he would briefly mention the 

 chief points. 



In the first place, the Society would be pleased to find that Pro- 

 fessor Abbe had given full credit to England, and to this Society in 

 particular, in regard to the origination of these objectives, his paper 

 read before the Jena Society being entitled " On Stephenson's System 

 of Homogeneous Immersion for Microscope Objectives." 



Professor Abbe had also turned his attention to finding aqueous fluids 

 fit for homogeneous immersion, and believed that " distilled chloride of 

 zinc dissolved in water will prove to be an excellent substitute for tho 

 oil of cedar wood. It does not dissolve balsam, and can be cleared 

 off by water, and does not flow like the cedar-oil ; its consistence is 

 like thick olive oil." Professor Abbe added that he is making experi- 

 ments with other preparations, from wliich he expects good results. 



A third point related to a suggestion recently made by Mr. 

 Stephenson that, looking to the large working distance of the oil- 

 immersion system and the optical homogeaeity of crown glass and the 

 immersion fluid, the front lens of the objectives, instead of being held 



