REVIEWS — A HISTORY OF INFUSORIA. 369 



has not a well-defined field, and is not exactly adapted to students of 

 any one department. Yet we believe, that having produced such a 

 work as was contained in his previous editions, and desiring to carry 

 on his labours in the same direction, our author could not have done 

 better than adopt the plan which he has followed out, as he has se- 

 cured able assistance in the several departments, and given a great 

 mass of useful and interesting information. We must accept of what 

 he has done as a valuable contribution to science, of great practical 

 use to a large class of investigators, although we feel both the defi- 

 ciencies and the evils arising from a too great mixture of subjects, 

 and may be disposed to recommend special treatises on the different 

 subjects here brought together, as most likely to promote the progress 

 of knowledge and meet the wants of the students of Nature. 



Our author divides his treatise into two parts. 1st. A general 

 history of Infusoria, &c., in which their nature, structure, functions, 

 and classification are considered; 2ad. A systematic treatise, in which 

 the families, genera, and species are enumerated and characterized. 

 The first part commences with Ehrenberg's Bacillariae, containing 

 Desmidiaceae, Pediastreae (doubtfully separated from the preceding), 

 and Diatomaceae. All these are now very properly treated as vege- 

 tables. Perhaps Ehrenberg's name would have been better entirely 

 laid aside, as it was connected with the notion of their animal nature ; 

 and as the several orders, if more nearly connected with each other 

 than with some other Algae, will form one alliance which should be 

 named according to Lindley's plan. The account of the present state 

 of our knowledge of these orders appears to us to be very satisfactory, 

 and affords great advantages to any one entering upon their study. 



The second section is devoted to what are here called Phytozoa, — a 

 term intended to express a mixed animal and vegetable nature, under 

 which are included a large part of Ehrenberg's Anentera. The group 

 is a very miscellaneous one, and confessedly not natural. We give the 

 author's reasons for adopting it, in his own words : " In the opinion 

 of the majority of modern writers, the Phytozoa are in general un- 

 distinguishable from unicellular Algae, among the different families of 

 which they consequently seek to distribute them ; and doubtless the 

 creation of such a group is pu.rely artificial, and cannot be admitted in 

 any attempted philosophical or natural classification of microscopic 

 organisms. However, since so much uncertainty and dispute still 

 prevail on the question of the animal or vegetable nature of very 



