28 Prof. P. T. Cleve and ^h: C. Meresclikowsky on 



number of interesting and, in the great majority of cases, 

 correctly described facts concerning the cell-contents of the 

 diatoms surpasses all that has been done before. 



It is the recognition of the great value of this work and 

 the desire to render it still moi*e valuable and useful, not for 

 finding errors, that has induced us to undertake the publica- 

 tion of the following critical remarks. Mistakes are inevit- 

 able in a work of such great extent and on a subject so 

 delicate and so full of difficulties. We believe therefore that 

 our criticism, undertaken in a friendly spirit and for the sake 

 of truth only, will by no means wound the feelings of the 

 author. 



One of us (Cleve) will endeavour to correct as far as possible 

 the errors in the determination of species, the other will deal 

 more particularly with the cell-contents. 

 February 5, 1902. 



A. Notes hy P. T. Cleve. 

 Asterionella Bleakeleyi (p. 2S) is a tropical species. The 

 specimens figured agree with Diatoma (enue, Ag., a common 

 freshwater form frequently occurring in slightly brackish 

 water. 



Navicula retusa (p. 47). — The figure shows that the median 

 strife are alternately longer and shorter, a characteristic that 

 does not belong to the named species. Doubtless Navicula 

 digito-radiata (var. cyprinus). 



Navicula subtilis (p. 53) does not represent Gregory's 

 species, but rather JSavicula cincta. 



Navicula ammophila var. lata (p. 54) is too large to be a 

 form of N. ammophila. 



Navicula neglecta (p. 57) is said to be akin to N. formosa^ 

 but I have never met with so coarsely striate a form (striai 

 6-7 in 0-01 mm.). 



Navicula latissima var. constricta (p. 57) is a form of 

 N. humei'osa. 



Navicula pygmaea (p. 59) = N. forcipata, Grev. 



Navicula Graeffii (p. 60) seems to represent a form of 

 Diploneis fusca. Grunow's N. Grceffii occurs in tropical 

 seas only. 



Navicula interrupta (p. 61) probably represents a form of 

 l)ip)loneis splendida or D. bombus, D. interrupta has no striee 



