liihliographical Notice. 391 



earth in geograpliical regions and provinoes, like otlicr created beings; 

 and lie takes this opportunity of introducing the very weighty re- 

 mark, that he cannot conceive " liow moral j)hilosophers, who urge 

 the unity of the origin of Man .is one of the fundamental principles 

 of their religion, can at the same time justify the necessity which it 

 involves of a sexual intercourse between the nearest blood- relations 

 of that assumed first and unique human family." We may say, 

 however, that though he enlarges nmch upon the characters of spe- 

 cies, and goes fully into the methods of discovering them, we wait still 

 for a perfect solution of the celebrated * crux'' " what IS a species ?," 

 to which we find no satisfactory answer here given. There is, how- 

 ever, very much that is wortliy of serious attention in this chapter 

 concerning the true method of investigation ; and were these or 

 similar rules (if these rules are not right) established and followed, 

 there would be less cause for the well-grounded complaint, that in 

 almost every " characterization of genera, of families, of orders, of 

 classes, of types," "characters of the same /cind are introduced 

 almost indiscriminately to distinguish all these groups." 



The introductory essay concludes with a chapter on the principal 

 systems of Zoologj', in the first part of which Prof. Agassiz gives us 

 his own views. Like other distinguished naturalists of the present 

 da}', he is disposed to return to the fourfold division of the great 

 Cuvier, as modified by modern investigators, and considers the P?-o- 

 tozoa [?] an unnatural combination of the most heterogeneous beings, 

 " to be dinded partly among plants and partly among animals, in the 

 classes of Acephala, Worms and Crustacea." The Radiates he 

 divides into Polypi, Acalephce and Echinoderms ; the Mollusks 

 into Acephala, Gasteropoda and Cephalopoda ; the Articulata 

 into Worms, Crustaceans and Insects. In the Vertebrates he 

 maintains that the number and limits of the classes are not yet sa- 

 tisfactorily ascertained, but is inclined to separate them as follows 

 into no less than eight (!) divisions : — 



1. Myzontes (Myxinoids and Cyclostomes). 



2. Fishes proper (Ctenoids and Cycloids). 



3. Ganoids (Coelacanths, Acipenseroids, Sauroids, and doubtful, 



Siluroids, Plectognaths and Leptobranches). 



4. Selachians (Chimserse, Galeodes and Batides). 



5. Amphibians (Cscciliae, Ichthyodi and Anura). 



6. Reptiles (Serpentes, Saurii, Rhizodontes and Testudinata). 



7. Birds (Natatores, Gralhc, Rasores and Insessores). 



8. Mammals (Marsupialia, Herbivora and Carnivora). 



It would not be difficult to pick holes in this portion of Professor 

 Agassiz's arrangement, particularly as relates to the two latter classes, 

 and the author himself submits his views "rather as suggestions for 

 future researches than as matured results." 



The second part of the work — " On North American Testudinata" 



19* 



