1894 THE MICROSCOPE. 149 



If I use pungent English in thus expressing my per- 

 sonal opinion, it is not that I have any unfriendly feel- 

 ing toward Mr. Cunningham, for whom" I have nothing 

 but respect, and the greatest commiseration in the for- 

 midable task that he has set for himself; it is not be- 

 cause I think him wrong in his conclusions ; nor that I 

 am anxious to appear in print with harsh criticism, as I 

 am not, for I have asked the editor to destroy my manu- 

 script if any other person has enough interest in the sub- 

 ject to call attention to Mr. Cunningham's reprehensible 

 method of illumination, especially reprehensible when he 

 is laboring to overthrow the accepted teaching of the 

 most learned specialists. He may have proved what he 

 claims. I do not think he has ; but aside from this part 

 of the subject, the methods of illumination by which he 

 arrived at his conclusions are open to the gravest criti- 

 cism, and the results obtained in such circumstances, al- 

 ways remembering Mr. Cunningham's purpose, are to be 

 considered, even slightly, only after he has corrected 

 what must have been an oversight, an omission made 

 when his thoughts were busy with an observation that 

 might be a startling discovery, and result in the trans- 

 ferring of a great group from one natural kingdom to 

 another. Microscopical objects used avS a basis for asser- 

 tions as important as Mr. Cunningham's would be if they 

 were proved, demand, in these days, not only the most 

 careful illumination with the best optical appliances, but 

 the results must be almost worthless unless the observa- 

 tions are made with wide-angled, oil-immersion objec- 

 tives, with an achromatic condenser having a numerical 

 aperture approximating that of the objective used, and 

 perhaps with compensating eye-pieces, certainly not with 

 an old-fashioned, half-inch objective reversed and em- 

 ployed as an ocular. And why Mr. Cunningham shoulp 

 use grass-green glass and condemn blue glass which, 

 when of the proper shade, is commended by microscop- 

 ists the world over, I do not comprehend. 



