IGO SMITH, ON BRITISH DIATOMACE.E. 



intermediate stages, but, in particular, also are the anatomi- 

 cal, physical, and chemical conditions of the younger Empusa- 

 forms, which appear in all respects to present the characters, 

 not of spores, but of young, newly formed cells. Further 

 researches are requisite to bring this question to a satisfac- 

 tory determination. 



A Synopsis of the British Diatomacece. By William Smith, 

 F.L.S. London : Smith and Beck, and Van Voorst. 



Those microscopists who are working at the British Dia- 

 tomacese will rejoice to know that the second volume of 

 Professor Smith's w^ork is at last completed. They have now 

 a complete work to which they may refer for information 

 with regard to all forms of British Diatomaceae. This 

 second volume is a worthy companion of the first. The 

 descriptions of the species are ample, the notes are valuable, 

 and the plates, if possible, exceed the last in their beauty 

 and accui^acy. With regard to the latter, we are sure that 

 Professor Smith would be amongst the first to acknowledge 

 how greatly the value of his work is enhanced by the unri- 

 valled skill with which Mr. Tufi'en West has delineated the 

 beautiful objects he has described. 



Since the publication of the first volume in 1853, many 

 new species belonging to genera there described have been 

 discovered ; and although Professor Smith has given a list of 

 those in an appendix, with references to the works in which 

 they are described, mostly in our own Journal, yet every 

 one will be glad to hear that he intends publishing a Supple- 

 ment. Many of the new species require criticism and revi- 

 sion, and a Supplement will afford Professor Smith an oppor- 

 tunit}' of not only hauling over the contributions of his friends, 

 but some of his own. 



The Introduction to the present volume contains some 

 interesting remarks on the history of the Diatomaceae. The 

 first section takes up the question of reproduction. Little 

 seems to be added as to the nature of this process, since the 

 first observations of Mr. Thwaites. The fact of the produc- 

 tion of the spore as the result of conjugation has, however, 

 been observed up to the present time in no less than thirty- 

 two species, belonging to seventeen genera. Of these, Pro- 

 fessor Smith gives a list. On the modifications of this pro- 

 cess. Professor Smith makes the following remarks : 



" I. We have two parent-frustules, and two sporangia as 



