78 The Microscope. 



trace of the pencil marks was left, and then the surface could 

 be gone over with any of the aniline dyes, largely diluted, so as 

 to represent the ground work of the stain, and the medullated 

 fibres and the ganglionic cells filled in respectively with black 

 and red ink. With the apparatus specimens colored with dark 

 stains will give a more clearly differentiated picture than the 

 light ones. 



The instrument has been made for me by E. B. Meyrowitz 

 New York, and is to be had with two or three lenses, two are all 

 that are necessary ordinarily, but the third is useful sometimes 

 when the object to be drawn is small and where you desire high 

 magnification. 



NOTES OF THE DIATOMS OF THE FLORIDA COAST. 



CORNELIUS ONDERDONK. 



One of the commonest forms on the Florida coast is the one 

 wrongly classed as Eupodiscus radiatus. It is evident that this 

 Diatom was classed with E. argus wholly on account of the four 

 short processes called spines, while the structure of the entire 

 valve was ignored. It is evident to the careful student that the 

 structure has much to do with the life of the organism, while a 

 mere spine is of small importance. The structure of E. radiatus 

 is identical with the most common forms of the Coscinodisceae, 

 viz., a sharply cut, purely siliceous hexagonal network, over 

 which is laid a membrane containing areolar indentations, whose 

 positions correspond with the hexagons of the frame work. The 

 structure of E. argus is totally different. It seems that writers 

 have found diflficulty in determining the structure of this form. 

 I presume they worked with the fossil specimens, for no diffi- 

 culty is to be found when one examines a number of specimens 

 from the Florida waters. 



The frame work is a robust, irregular net work (never hexa- 

 gonal), nearly purely siliceous in small forms, but ochreous, 

 and heavy with what I will call an argelaceous deposit in the 

 large opaque forms. If one examines a number of frustules one 

 will find portions from which the semi opaque deposit is re- 

 moved, leaving the siliceous net work sharply defined. The 

 lining membrane has minute dots placed in radial lines without 



