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Cii. XLII.] 



CONCLUDING EEJVlARKS ON EXTINCTION. 



401 



nutioii or tlie entire extirpation of some other, and must 



maintain its ground by a snccessful strnggle 



against tlie 



encroachments of other plants and animals. That minute 

 parasitic plant, called ' the rust ' in wheat, has, like the Hes- 

 sian fly, the locust, and the aphis, caused famines ere nov/ 

 amongst the ' lords of the creation.' The most insignificant and 

 diminutive species, whether in the animal or vegetable king- 

 dom, have each slaughtered their thousands, as they dissemi- 

 nated themselves over the globe, as well as the lion, when 

 first it spread itself over the tropical regions of Africa. 



Concluding remarJcs on extinction. — From what has now been 

 said of the effect of changes which are always going on in the 

 condition of the habitable surface of the globe, and the 



e constantly extending their 



some 



clx 



may 



s a co- 



rollary, tliat tlie species existing at any particular period, 



in the course of ages, become extinct one after tlie 



must, 

 other. 



must 



sion from Bufion, 'because Time fights against them.' 



If such then be a law of the organic world, if every species 

 is continually losing some of its varieties and every genus 

 some of its species, it follows that the transitional links which 

 once, according to the doctrine of Transmutation, must have 

 existed, will, in the great majority of cases, be missing. We 



om 



fc3 



O 



finite lapse of ages the whole animate creation has been 



decimated again and again, 

 tive alone remains of a tvD 



ometimes 



V7"e rarely find 



fossil sp'ecies may be reckoned by hundreds. 



that whole orders have disappeared, yet even this is notably 



the case in the class of reptiles, v»^hich has lost some orders 



characterised by a higher organisation than any now surviving 



in that class. Certain genera of plants and 



seem to have been wholly wanting, and others which Avere 



feebly represented, in the Tertiary Period, are now rich in 



species, and appear to be in such perfect harmony with the 



present conditions of existence, that they present us w^ith 



anima 



countless varieties confounding the zoologist or botanist Vvdio 

 undertakes to describe and classify them. 



