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HYrOTHP:SIS OF THE DEVELOPjMEXT 



OF THE VEGETABLE AND ANIMAL KINGDOMS. 



It has been already intimated, as a general fact, that 

 there is an obvious gradation amongst the famiUes of 

 both the vegetable and animal kingdoms, from the simple 

 lichen and animalcule respectively, up to the highest 

 order of dicotyledonous trees and the mammalia. Con- 

 fining our attention, in the meantime, to the animal 

 kingdom — it does not appear that this gradation passes 

 along one line, on Avliich every form of animal life can 

 be, as it were, strung. There seems to be a plurality of 

 lines ; how many there are it is not necessary at present 

 to decide. There may be two or more lines ; or the lines 

 may be branching ; or the whole may be in a circle com- 

 posed of minor circles, as has been recently suggested. 

 But still it is incontestable that there are general appear- 

 ances of a scale beginning with the simple and advancing 

 to the complicated. The animal kingdom was divided by 

 Cuvier into four sub-kingdoms, or divisions, and these 

 exhibit an unequivocal gradation in the order in which 

 they are here enumerated : — 



Kadiata (polypes, «S:c.). 



MuLLU.scA (pulpy animals). Akticulata (jointed animals). 



Vertebuata (animals with internal skeleton) ; 



