REVIEWS — PRINCIPLES OF ORGANIC ARCHITECTURE. 279 



the common plan which runs through extensive groups and the man- 

 ner in -which comparatively slight variations are made to fit each for 

 its destined condition. The subject is interesting and important, 

 the author's style clear, correct, and pleasing, and the numerous il- 

 lustrations afford great assistance to the reader, so that although the 

 work pretends to no novelty, it promises much utility, and deserves 

 to be recommended to all who desire to comprehend the great prin- 

 ciples and general results of Zoological Science. 



In giving an outline of Zoological classification, it would in our 

 opinion have been an improvement, if our author had made Protozoa 

 a fifth sub-kingdom containing the classes Porifera, Ehizopoda, and 

 Infusoria ; and notwithstanding the close relationship of Polypifera 

 and Acalephae forming Mr. Huxley's Coelentebata, it might be 

 as well at present to keep them separate as classes with Echinoder- 

 mata of the Eadiate sub-kingdom. Among Yertebrata there ought 

 to be no hesitation in distinguishing five classes, Fishes, Amphibia, 

 iReptilia, Birds, and Mammalia. There is without doubt a consider- 

 able external resemblance between Amphibia and some Reptilia, but 

 the Anallantoidian embryo; the naked surface; the two modes of 

 respiration in most species, at least in some stages of their existence, 

 most of them passing through metamorphosis ; the absence of ribs, 

 and. some other anatomical particulars, form perhaps as good charac- 

 ters for a class as those which distinguish other received classes and 

 justify the eminent naturalists who assign a fifth class to Yertebrata. 



We may possibly be somewhat influenced in this decision by a fancy 

 that we have found natural and good divisions in all parts of the 

 animal kingdom, falling into the numbers three or five. It seems to 

 us that there is something in this of a general law. Under each type 

 we have a group expressing its lowest degree of development, one 

 expressing the predominance of the functions of vegetative life, and 

 one in which the functions of animal life take the lead. Each of the 

 two latter however, naturally sub-divides, at least in all the higher 

 divisions into two, expressive of different variations in the destined 

 mode of life. In the last mentioned divison, one for example, will 

 display more of power or fierceness, another more of vivacity and 

 activity. In the greater natural divisions we sometimes think we 

 observe a nucleus or central group, peculiarly typical, around which 

 the five leading modifications dispose themselves. Beyond this, we 

 know of no deviations from the above mentioned numbers which we 



