206 The Microscope. 



of the stain, in the case of the diatoms with strong motion, and 

 least manifest in the case of fixed diatoms like those with stipes ; 

 that the diatomaceae have no internal motion analogous to the 

 motion called cyclosis in the Desmidaceae; that the motion on 

 the outside of the outer covering of the Diatomaceae is strongly 

 analogous to the motion on the inside of the outer covering of 

 the Desmidaceae. 



From the above mentioned facts and others which time for- 

 bids to mention, I offer as a theory that the motion of the dia- 

 tomaceae is caused by what I will call external cyclosis. I do not 

 court credence, (an editor of a journal in the cause of microscopy 

 objected to my papers on the ground that I could not expect to 

 gain credence), I only trust microscopists will investigate ; if my 

 theory is false, let it fall. 



[The author of this paper wishes it stated that he uses a 

 Gundlach 1-5 of 135°, and Gundlach i Im. 140° N. A., with an 

 amplification to 2,500 diameter. His investigations, he says, have 

 extended upwards of five years. — Ed.] 



Just after our August issue had gone to press we learned 

 of the death of Dr. Thad. S. Up de Graff, of Elmira, N. Y. In 

 our next issue Dr. Lewis M. Eastman, of Baltimore, will con- 

 tribute a paper on his life and work. 



During the past two months we have been enjoying a va- 

 cation from the more active duties of college life. Some of our 

 correspondents are aware of this, we fear, because of neglect 

 on our part to reply to their queries or correct some oversight 

 in our mailing list. We desire that all our subscribers should 

 feel well satisfied with us, and if the journal fails to reach you, 

 or if it comes in a damaged condition, just let us know and the 

 error will be corrected if possible. 



Mr. H. H. Turner represented the Gundlach Optical Co. 

 at Cleveland and exhibited, principally, some of the new 

 lenses of Mr. Gundlach. These always excite great interest 

 among all advanced workers. 



