407 



MOTES ON SOME INTERMEDIATE FORMS OF THE 

 GENERA NAVICULA AND CYMBELLA. 



By Sir Nicholas Yermoloff, K.C.B., K.C.V.O., F.R.M.S, 



{Read April 9th, 1918.) 

 Plates 26-28. 



All students of Diatoms are invariably impressed by the immense 

 number of individual forms, species, sub-species and varieties 

 patiently noted, described, named and classified. The differences 

 of diagnosis which have led to the creation of new forms are 

 undoubtedly sometimes very trifling and uncertain, based upon 

 personal impressions of observers, and, together with the enormous 

 multiplication of forms, there has arisen a veritable labyrinth of 

 confused synonymy. 



From time to time, distinguished authors have tried to remedy 

 this state of things and to put some order in this chaos, striving 

 to reduce the existing number of admitted species and varieties, 

 and basing the regrouping they proposed, not so much on indi- 

 vidual variations as upon similarities of forms. Such regroupings 

 have been attempted by Cleve as regards the genus Navicula, by 

 Cox and Kattray as regards Coscinodiscus. 



It cannot be admitted that these attempts have until now 

 proved very successful and fruitful. On the pages of one of 

 such recent reformers we read : " The reduction of the enormous 

 catalogues of species of Diatomaceae is a consummation devoutly 

 to be wished." 



Well, perhaps I am mistaken, but I am not so sure that this 

 consummation is so devoutly to be wished as all that : it seems 

 to me that the admirably patient and careful labour of registering 

 minutiae, and the consequent subdivision of species, has been 

 both fruitful and inevitable. It has been — to borrow a term 

 from higher mathematics — a process of " differentiation," a study 

 and investigation of the elemental variations of the so-called 



JouEN. Q. M. C, Series II.— No. 83. 31 



