1893.] NEW-YORK MICROSCOPICAL SOCIETY. 103 



Diatomaceae, as a purely scientific pursuit or pastime, for the 

 past fifteen years. If the aggregate result of one's efforts in any 

 line of study is of any value, it certainly entitles him to enter the 

 field of generalization, if he finds a reasonable or substantial 

 basis to induce such action. 



To within about a year ago I felt satisfied with the common- 

 ly conceded position of the Diatomaceae among the unicellular 

 algae, and assigned them to the vegetable kingdom in prefer- 

 ence to the animal kingdom. Less than a year ago Dr. Arthur 

 Mead Edwards, in a letter to me, propounded the query, *' What 

 is a diatom ?" and also answered his own question by saying, " I 

 believe that the Diatomaceae are the Protista." Through an im- 

 politic impulse I replied that it would scarcely be possible to ad- 

 mit that the diatoms were other than " unicellular plants." When, 

 in order to substantiate his conception of their animal characters, 

 he announced in a microscopical journal that he had actually 

 seen the animal occupant of a frustule of Coletonema eximium 

 leave and re-enter its shell on several occasions, I wrote him that 

 the species of that name were so small that it would seem hope- 

 less to take that view of one of the smallest among the genus 

 Pleurosigma. When we mention the name of this eminent phy- 

 sician, who has devoted forty years of his life to the study of the 

 Diatomaceae, and who might justly be styled the Nestor of Ameri- 

 can diatomists, he must be credited with valid reasons for refus- 

 ing to accept the diatoms as single-celled plants, and for using his 

 abilities in opposition to the continuance of such a view. 



I would feel better satisfied to have the station of the Diatoma- 

 ceae removed from the domain of doubt which surrounds their 

 position, by irrefragable proof. I would be more contented in re- 

 alizing that this special class of animated matter was ranged 

 with animal life rather than with' plant life. It would tone down 

 and remove from the realm of triviality the enthusiasm of those 

 whose mind has become captivated with the beauty and mystery 

 attached by the Creator to this mystical unit of the universe. If 

 genius could demonstrate beyond cavil the ajiimal nature of the 

 Diatomaceae, then one would find the objects of his favorite 

 study placed a scale higher than the simple Amoeba and in near 

 relation to the beautiful Radiolaria. Who will undertake to ex- 

 plain why the Diatomaceae so strongly appeal to intellectual 



