1894 THE MICROSCOPE. 147 



proved that animality, I do not hesitate to say that in 

 my opinion he has done uotliing of the kind. He entitles 

 his paper "The Diatom Considered as a Protozoan, with 

 Method of Demonstration," and says, on page 231 of the 

 31icroscopical Journal for August last, that if certain 

 events had not occurred "I would have had to continue in 

 the mental attitude of one who strongly suspects the 

 animal character of the motile diatoms, but cannot crys- 

 tallize his proof into a concrete expression for lack of 

 demonstrable evidence. But this stage has been safely 

 passed and an easy method of verification is accessible 

 to all who use the microscope as an instrument of re- 

 search, or for biological studies of any kind." If this 

 and his title mean what they seem to say, then Mr. Cun- 

 ningham asserts that he has proved the diatom to be an 

 animal, and that any one accustomed to the use of the 

 microscope can repeat that proof. Mr. Cunningham de- 

 serves credit for the courage that supports him in the 

 publishing of these convictions. 



But personally, I should have read his interesting arti- 

 cle with more confidence, if he had not been so careful 

 to explain his method of illuminating the instrument and 

 of using the condenser. His explanations of these points 

 vitiate his entire paper, and render almost worthless what 

 otherwise might have merited some consideration. 



For the elucidation, and especially for the teaching of 

 such fine points as Mr. Cunningham has undertaken to 

 demonstrate, nothing* short of what is called critical il- 

 lumination and the production of the critical image, 

 should have received his earliest attention. On the con- 

 trary, by his own showing, he has examined his speci- 

 mens in what is describable only as an optical mess; he 

 then says that he has proved the animality of the dia- 

 tom, and seems to expect the readers of this Journal to 

 accept his teaching in opposition to what has stood the 

 test, and been universally received, for years. 



