Bibliographical Notices. 141 



of preserving specimens for microscopical observation which has 

 been so extensively and successfully carried out by Mr. Thwaites, 

 &c, for information on which we must refer our readers to the work 

 itself. The long extract we have given will sufficiently show the 

 style and powers of reasoning of our author. The introduction was 

 unfortunately written and printed before the descriptive matter, 

 which precluded the possibility of putting the last finishing touch, 

 on the completion of the work, which is often of such immense 

 value in giving the proper effect to the whole. It is impossible to 

 read it without feeling this, especially as the brilliant discoveries of 

 Mr. Thwaites on the conjugation of Diatomacece were made before 

 the publication of the volume, and which would have given Mr. 

 Ralfs new ground for thought and comparison, discoveries now ex- 

 tended to the spores of Palmella. . 



Of the general execution of the work we cannot speak too highly : 

 the descriptions are accurate and copious, the species well-defined, 

 the synonyms carefully scrutinized, every available source of infor- 

 mation ransacked, and the figures, for which it is principally in- 

 debted to Mr. Jenner, beautiful and accurate. The whole tone of 

 the book too is exactly that manly tone at once of modest candour 

 and of self-respect, which shows the faithful and conscientious ob- 

 server confident in his own carefulness and measure of ability, but 

 aware of the liability to error which is inseparable from man's 

 nature. 



It is a book not merely for the algologist but for the physiologist, 

 and in the spores of these curious productions the geologist will re- 

 cognise the bodies which are so prevalent in flints. Fossil fronds of 

 Desmidiece have been found by Professor Bailey, who detected various 

 species of Closterium and Euastrum in calcareous marls collected in 

 New Hampshire and New York by Professors Hubbard and Hall, and 

 also in marl at Scotch Town, New York, by Mr. Connors. Professor 

 Bailey informed Mr. Ralfs that the specimens from the last-named 

 station were taken from below the bones of Mastodon giganteus. As 

 sporangia of the Desmidiece and other membranous bodies in a fossil 

 state have lately been detected by Mr. Deane and Dr. G. Mantell in 

 the gray chalk of Folkestone, it is probable that a careful search in 

 that neighbourhood would also bring to light the fossil fronds of 

 Desmidiece. 



We are not aware that any Desmidiece have yet been found in 

 amber. A list of Diatomacece contained in that curious substance 

 was lately given in our Journal. These were communicated to 

 Ehrenberg by Dr. Thomas of Berlin, and specimens containing the 

 same species have been entrusted by Dr. Thomas to the writer of 

 these remarks ; but in a very extensive list of specimens prepared by 

 Dr. Thomas now in our hands, it does not appear that any Desmidiece 

 have yet been detected, nor is there any indication of the kind in the 

 work of Dr. Berendt. 



It remains only that we recommend most cordially the work of 

 Mr. Ralfs to the attention of our readers, assuring them that they 

 will not be disappointed in it ; and to express our hope that it will 

 shortly be followed by a similar volume on the Diatomacece. 



