PROCEEDINGS OP THE SOCIETY. 557 



it differing from the latter not only in its morphology, but in the fact 

 that it is not fatal to fowls. 



Mr. Dowdeswell said that the question of the specific identity of 

 organisms of this kind was as difficult as it was also important. Dr. 

 Sternberg was a great authority upon the subject, and his opinion 

 was entitled to great consideration. He thought that the additional 

 particulars now adduced, so far disposed of the question of identity 

 that he must accept the conclusions arrived at. 



The paper was further discussed by Mr. Michael and the President, 

 who referred to the death of Dr. T. K. Lewis, the discoverer of the 

 microbe of the human mouth. 



Mr. F. H. Evans exhibited some photo-micrographs produced by 

 the Woodbury-type procesp, from negatives taken by himself and 

 transferred to glass for the purposes of lantern illustration, and so 

 that in many cases the objects could be seen on the screen more 

 perfectly than under the Microscope. To show what an advance 

 had been made in this dii-ection, sixty of the slides were shown upon 

 a portable screen by Mr. George Smith (of the Sciopticon Company), 

 who had printed the slides from the original negatives. The objects 

 illustrated comprised Diatoms and Desmids, Foraminifera, Polycistina, 

 star-fish, sections of Echinus spines, insect preparations, animal 

 parasites, and anatomical and vegetable sections, the remarkable 

 clearness of most of the photographs calling forth frequent favourable 

 comments from the Fellows present. 



Mr. Evans, who had temporarily lost his voice, handed in the 

 following note from himself and Mr. Smith : — 



" These slides are intended specially for educational purposes, to 

 help the optical lantern to fulfil its manifest destiny as the great 

 educational demonstrating instrument of the future. 



They are not put forward as perfection, but as an earnest effort 

 towards the limit of perfection attainable by human skill. 



The measure of success already reached is controlled to a great 

 extent by the inherent imperfection of even the most skilfully con- 

 structed lenses ; but while the definition is possibly less perfect than 

 may be considered desirable, it is certainly not inferior to that obtain- 

 able by any ordinary high-class Microscope, while, if the degree of 

 magnification is taken into account, it is probable that it is not likely 

 to be greatly surpassed. It has also to some extent been controlled by 

 the character of the photographic plates in commercial use, which from 

 the exigences of the case have been necessarily employed — for while 

 rapidity is an extremely important feature of modern commercial 

 photography, the granular character of the sensitive film, apparently 

 almost inseparable from the enhanced rapidity, is decidedly inimical 

 to microscopic work, where structureless films are specially important. 

 It is a curious fact in the development and improvement of photo- 

 graphic processes that the important feature of structureless films 

 and development has been overlooked and neglected in favour of 

 rapidity, generally attended by granularity of the deposit. The wet- 

 collodion process with pyrogallic development, as given to the world 



