158 



THE AMEKICAN MONTHLY 



[August, 



in French, it will be found, we be- 

 lieve, quite practicable for those who 

 do not understand the language to 

 use the work for the identification of 

 species, since the words used in de- 

 scription are so nearly like the cor- 

 responding words in English. 



The first part of the volume is taken 

 up with a general account of the 

 diatoms — their structure, processes of 

 growth and multiplication, and the 

 methotls of studying, preparing, and 

 mounting them in difi'erent media. 



The arrangement of the systematic 

 part is, so far as our limited knowledge 

 of the subject enables us to judge, far 

 superior to any other classification we 

 have seen. The family is divided into 

 three sub-families, Raphides, Pseudo- 

 raphides, and Crypto-raphides. The 

 sub-families are then divided into 

 tribes, genera, and species. In each 

 case there is an analysis or synopsis 

 of the tribes, genera, and species, ar- 

 ranged like the key of a botanical text- 

 book, or like the synopses of genera 

 of algie in the ' Provisional Key to 

 Alga; of Fresh Water,' now being 

 published in this journal. The 

 genera and species are clearly de- 

 scribed, and references are given to 

 original descriptions and figures. 



We shall doubtless have occasion 

 to refer to some parts of this work 

 more at length in future. Hitherto 

 we have regarded the study of dia- 

 toms, at least the determination of 

 species if not also of genera, as some- 

 thing only possible after long study 

 and familiarity with the vainous 

 forms ; principally because the sub- 

 ject has seemed involved in such 

 hopeless confusion, with the valuable 

 literature so extensive and scattered, 

 and the synonymes confusing and al- 

 most endless. A careful examination 

 of the text now published leads us to 

 believe that Dr. Van Heurck has, 

 by his masterly treatment of this very 

 difficult subject, opened the way for 

 the quick determination of any species 

 described in his book. 



We believe that the publication of 

 this work marks an era in the study 



of the diatoms, from which great ad- 

 vances in our knowledge of these in- 

 teresting plants will begin. No stu- 

 dent need longer be deterred by want 

 of sufficient literature from undertak- 

 ing their study, for in this work alone 

 will be found all that is essential for 

 the determination of nearly all the 

 established species. Not all, to be 

 sure, since it is devoted especially to 

 the diatoms of Belgium ; but it is still 

 sufficiently comprehensive for use in 

 any part of the world. 



A naturalist not specially familiar 

 with the diatoms can now study his 

 own collections and compare the 

 species with those found in other lo- 

 calities, as it has never before been 

 possible. 



Subscribers to the plates have all 

 received notice by mail that the vol- 

 ume of text can be furnished on re- 

 ceipt of their orders. As only a lim- 

 ited number of copies has been re- 

 ceived orders should be sent promptly, 

 otherwise we may be obliged to hold 

 them until a second importation is re- 

 ceived. 



Microscopical Exhibitions. — 

 The letter of a correspondent upon 

 this subject, published in another 

 column, brings forward probably the 

 only valid arguments that can be urged 

 against the suggestions that have led 

 to his criticisms. Assuming that the 

 proposed plan is practicable — which 

 is a matter of uncertainty to us, except 

 in exceptional cases — the subject 

 seems worthy of further considera- 

 tion, and we would invite a free in- 

 terchange of opinions in our corres- 

 pondence column from readers who 

 are interested in it. Meanwhile, we 

 avail ourselves of this opportunity to 

 reply to our correspondent's objec- 

 tions, in order that the reader may 

 have a clearer idea of the subject as 

 it presents itself to us. 



Our suggestions were made rather 

 hastily, and, as was stated at the time, 

 without sufficient consideration to 

 enable us to present the details in a 

 satisfactory manner. The subject, 



