98 E. M. NELSON ON NAVICULA RHOMBOIDES AND ALLIED FORMS. 



It should be understood that this formula must not be read 

 as if it were a mathematical or physical law ; it is only meant 

 to be a numerical guide which will probably be found much 

 more useful for purposes of identification than any verbose or 

 vague description of a species. 



Formerly a biologist's stock-in-trade was a ready pen, a 

 vocabulary of dog Latin and bastard Greek, and a glorified 

 grandmother's magnifying-glass ; but we trust that that day is 

 past, and that something more is required of those who undertake 

 the work of naming and classifying the Diatomaceae. Hitherto 

 diatoms have been considered important mainly on account of 

 their extreme beauty and also as affording objects of interest to 

 dilettanti, but for real biological purposes they had scarcely any 

 place. The editor of a biological journal who would have grudged 

 the space for a single paragraph on diatoms would have willingly 

 found room for twenty pages of a smartly written essay on Eozoon 

 canadense ; but temjwra mutantur. Ifc is now recognised that 

 diatoms are to marine life what grass is to the land animals. A 

 diatom lives on the inorganic chemical substances in sea water 

 and so becomes suitable food for Copepods, etc., which in turn are 

 eaten by Crustacea, which constitute the food of large fishes. So 

 it appears that diatoms are of the highest importance to us even 

 from an economic point of view, for if we want good fishes we 

 must look after our diatoms. 



It is surprising how very little we really know about diatoms. 

 Hardly anything is known about their reproduction. One of the 

 most important papers on this subject was read at this club by 

 Mr. Buffham, and is printed in our journal.* Hardly anything 

 is known of their life-history. In those parts of the world where 

 one would expect to fi.nd them in great abundance they are com- 

 paratively few ; and in other places, where one would think that 

 they could not possibly live, they are to be found in enormous 

 numbers. We are still in total ignorance of the causes of their 

 movements. So then we may take it that the study of the 

 Diatomaceae is still in its infancy and, consequently, there is a 

 grand microscopic harvest waiting for an energetic Queketter to 

 reap. 



* Journ. Q.M.a, ser. 2, vol. 2, p. 131, pis. 7 and 8 (1885). 

 Journ. Quekett Microscopical Club, Ser. 2, Vol. XI., No. 67, November 1910. 



