66 



The Microscope. 



As the names for diatoms are gaining so fast, I have called this Cos. 

 excavatus, var. Grevilli, after the original discoverer. 



The next diatom to claim my time and attention was a very small 

 disk form having a perfect cellulate marginal rim, the center mark- 

 ings being of a perfect navicular form. Finding but one diatom at 



that time I looked it over 

 with care before mounting 

 it, to see if by chance it 

 could be a double frustule, 

 but finding it was not, I 

 mounted it alone on a 

 slide and some time after- 

 wards I sent it to my 

 friend Mr. C. Febiger, for 

 him to photogi'aph and 

 see what he thought of 

 it as a new find. His 

 answer was: "Focus up 

 or focus down, I cannot 

 separate what appears to 



R. Marylandica. be a double disk, SO T 



must think it only one frustule." Prof. H. L. Smith to whom I sent 

 a photograph, wrote me March 24: "Photo No. 2 is undoubtedly a 

 navicula, lodged inside another, a melosira — think you will find it a 

 double specimen, two differ- 

 ent diatoms.'' Being very 

 sure that I had a new 

 genus, I wrote him again 

 and he answered as follows : 

 " Am obliged for the photos 

 and am still of the opinion 

 that this one is an accidental 

 combination. A'"o genus df 

 the diatovis will take so 

 anomalous a form. Tiiie, 

 this does not prove any- 

 thing ; still there is a 

 hai-mony of structure in all 

 hitherto discovered that is 



decidedly against the in- k. Christianii. 



tegrity of this curious thing which you have photographed, 

 ever find another, look it over carefiUlv. 



If you 



