115^ 



Mr. Karop said it was certainly very curious to find tliat they 

 had never before had a paper on Entomostraca. When this was 

 mentioned to him he hardly credited the statement, but having 

 looked through the volumes of their " Proceedings," he was 

 obliged to come to the conclusion that such was the case. 



Mr. E. M. Nelson gave at some length a resume of his paper 

 on " The Optical Principles of Binoculars," dealing especially 

 with the apparent conflict of the opinions of Dr. Carpenter and. 

 Prof. Abbe upon the subject. 



The President said they were greatly indebted to Mr. Nelson 

 for this paper. He should not like, however, to express any 

 extended opinion upon it, because they had not heard it read in 

 its complete form, but he was quite sure that when they had it 

 before them they would find it well worth}' of careful reading. 

 The subject itself deserved more attention, because, from the 

 Abbe point of view, there was nothing left so unsatisfactorily 

 as this attempt to explain the optical theory of the binocular 

 microscope ; he should, therefore, have great pleasure in reading 

 the paper, and hoped it might be the means of giving a new 

 value to this form of instrument, for if only the prisms could 

 be made perfect, there was no reason why it should not be 

 possible to use it with much higher powers than hitherto. 



Mr. Karop said he could not quite understand the meaning 

 of the terms " inside and outside the pupil," and asked if Mr. 

 Nelson would explain them. 



Mr. Nelson said the words were not his ; he merely quoted 

 them from the paper, where it said that if you used one half of 

 the pupil you got one effect, but if you used the other half you 

 got the opposite effect. 



The President said the idea conveyed was the assumption 

 that the pupil was divisible into two halves ; and the effect 

 produced depended upon whether they took the rays which 

 came through the outer halves of the pupils or those which 

 came through the inner halves— whichever they took was said 

 to determine the result. 



Mr. Karop said he could not in that sense understand how 

 anything but confusion could result, because the perfection of 

 the visual image must depend upon the image falling on corre- 

 sponding parts of the retinae of the two eyes — that was, of 

 course, upon the outer side of one eye and the inner side of the 



