REVIEWS — A HISTORY OF INFUSORIA. 371 



great merit of the work is as an abstract and summary of what has 

 been done upon an extensive and most curious subject of inquiry, and 

 in consequence of this merit, no worker with the microscope would 

 willingly remain without it. The perfection of his means for obser- 

 ving minute objects is to little purpose if he cannot assign to them a 

 position, and obtain some insight into what is known or believed of 

 their nature and affinities, and he could scarcely find elsewhere anj 

 similar collection of the objects which may occur to his notice. 



The fourth section is devoted to Rotatoria or Rotifera, the wheel 

 animalcules, and contains a full and highly interesting account of their 

 Btructure, mode of life, and the various plans proposed for their classi- 

 fication. The discussion respecting their affinities is given at some 

 length. We have the arguments of Ley dig to prove them to be a 

 section of Crustacea ; the reply of Vogt, maintaining their connection 

 with Vermes; the speculation of Gosse, on their resemblance to in- 

 sects, which we must regard as very fanciful ; and the novel view of 

 Huxley, according to which we are to place them with Annelida, 

 Echinodermata, Trematoda, Turbellaria, and Nematoidea, as a group 

 of the lower Annulosa, under the name of Annuloida, Believing that 

 we are justified in maintaining Cuvier's sub-kingdoms of Articulata 

 and Radiafa, notwithstanding the great changes recently proposed, 

 that on the one hand Coelenterata is entirely unnatural, and on the 

 other hand the separation of the jointed-limbed from other articulated 

 animals is unjustifiable, we agree both with Leydig and Vogt in con- 

 sidering the Rotifera as exhibiting an articulate structure, though of 

 the lowest character, and we would settle the dispute as to whether 

 they belong to Crustacea or Annulata, by making them a distinct 

 class of the articulate sub-kingdom, which will thus contain : 1. Arach- 

 nida ; 2. Insecta, of which AJyriapoda is to be accounted a sub-class ; 

 3. Crustacea, including Cirrhopoda ; 4. Annulata, of winch. JSntozoa 

 constitute a sub-class ; 5. Rotifera, which, as the lowest form of the 

 articulate series, exhibit analogies with the lowest mollusca {Polyzoa) 

 and with embryonic states of the higher Radiata as well as with 

 I'rotozoa. 



Another short section, the fifth, is devoted to the Tardigrada, 

 which are, we think, rightly treated as a very low form of Arachnida. 

 In all the classes of articulate animals, whilst a common type may, in 

 our opinion, be well recognised, the range of development is very ex- 

 tensive and varied, so that animals of very low organisation appear 



