Edwards.] 258 [May 17, 



satisfactory a manner, by reference to plates. Thus in the case of 

 many of Ehrenberg's species, the descriptions are often so inaccurate 

 that the student can hardly tell what that author means, and must be 

 excused, if thereafter it should be discovered he has redescribed and 

 renamed any of them. And this is more particularly the case with 

 such forms as he examined in the recent condition. With his fossil 

 species, however, in most cases there is not so much difficulty of iden- 

 tification, as it is but necessary to obtain a portion of the same deposit 

 as he has examined, and in many instances there is no very great 

 difficulty in so doing, and there can generally be detected any form 

 on which he has bestowed a particular appellation. Thereafter, it 

 lies with the careful student to determine if the species be good or not; 

 and he can satisfy his mind as to whether the name given to it should 

 be retained. Unfortunately, however, Ehrenberg has occasionally 

 bestowed the same name on two, or even more, totally different spe- 

 cies, or, what is quite as bad, if not worse, given two or more names 

 at different times to the same species. In truth, the otherwise great 

 value that would have attached to his contributions to this branch of 

 knowledge, is very materially lessened by these facts, and students 

 are compelled either to stretch their consciences to their utmost ca- 

 pacity, or to ignore altogether what he has done in many directions. 

 I instance Ehrenberg, as he has bestowed names upon a much larger 

 number of forms than any other observer, and was almost the first to 

 call attention to the beauty of structure exhibited in the siliceous 

 epidermes of these remarkable plants. Many of the errors he has 

 fallen into have, however, plainly occurred from the defective instru- 

 ments of research at his command, at the time his investigations 

 were made. Some of our later students have, nevertheless, at times, 

 fallen into equal error, and in their case there is not so much 

 excuse ; for the rule above quoted, and which seems to be so very 

 sensible upon the face of it, has not been even taken into considera- 

 tion by those who appear otherwise to be very careful investigators. 

 One example in illustration will suffice. Thus, on examining W. 

 Smith's very elaborate and beautifully illustrated Synopsis of the 

 British Diatomacese, we find him naming a species of the genus 

 Epithemia as Argus, acknowledging at the same time that it had been 

 previously described as Epithemia alpestris by Kiitzing ; ignoring 

 entirely that already established name, for no sufficient reason, but 

 apparently because he, Smith, wished to apply the name Alpestris to 

 what he considered a new form he had discovered. - The confusion 



