36 Prof. P. T. Cleve and Mr. C. Mereschkowsky on 



are so different that they no doubt represent very distinct 

 species. This would explain the difference in tlie present 

 case, which is analogous to tiiat of Navicula scopulorum. 



But when Karsten describes the endochrome as being 

 composed of a single plate he is certainly wrong. I have 

 carefully studied over fifty species and varieties of Nitzschia, 

 and I can ]:iositively affirm that there is not a single species 

 of this genus which has less tlian two plates. All the state- 

 ments to the contrary are positively erroneous. This error, 

 introduced by Pfitzer, has since been frequently repeated with 

 a remarkable ]iersistency by Paul Petit, Van Heurck (' A 

 Treat, on the Diat.' p. 382), &c., and now again by Karsten. 

 There is no such thing as a single plate in tlie genus 

 Nitzschm, 



Tiiat is the reason why I do not believe the llantzscJiia 

 marina^ which, according to Karsten (see Amphora gamma, 

 ]). 108), possesses a single plate, to be a Hantzschia or to 

 belong to the Nitzschiete at all. It is, in my opinion, nothing 

 but an Epithemia, and therefore belongs to the Arcliaidege *, 

 which are usually characterized by a single plate [Auricula, 

 Av}2)h{prora^ . Its name should be changed into Epithem,ia 

 marina. 



Karsten also erroneously attributes one plate to Nitzschia 

 punctata, var. elongata (p. 121), N. litoralis (p. 121), and 

 N. constricta (p. 122). 



Nitzschia lanceolata, VV. Sm. (p. 129). 



We somewhat disagree in regard to this species. One of 

 us must have made an error in the determination, but I could 

 not say positively whether it is Karsten or myself. 



Surirella gemma, Ehr. (p. 131). 



The figure is correct, but it is not quite exact to say that 

 there are two plates. There is only a single plate, bent at 

 the lower end, and it is only before tlie division of thefrustule 

 that the plate becomes divided. 



2. C. Mereschkowsky. " Etudes sur I'Endochrome des 

 Diatom^es." 1^ Partie. Memoires de I'Acad^mie 

 Imp^riale des Sciences de St. Petersbourg, 1901, 

 vol. xi. n. 6. 



Tins paper contains a number of erroneous determinations, 



* See mv paper "On StcmroneUaj^ Ann. & Map. Nat. lli.-^t. vul. viii. 

 p. 429. 



