2G8 



EKOCCHI ON THE DYING OUT OF SPECIES. 



[Ch. XXXV. 



to tlie extermination of others ; and as these would dis- 

 appear gradually and singly from tlie scene^ I suggested 

 that probably the coming in of new species would in like 

 manner be successive^ and that there was no geological sanc- 

 tion for the favourite doctrine of some theorists^ that large 

 assemblages of new forms had been ushered in at once to 

 compensate for the sudden removal of many others from the 



scene. 



Brocchi on the dying out of a species. — An Italian geologist, 



Brocchi, the author in 1814 of an able work on the fossil 

 shells of the Subapennine Hills, endeavoured to imagine 

 some regular and constant law by which species might 

 be made to disappear from the earth gradually and in suc- 

 cession. The death, he suggested, of a species might depend, 

 like that of individuals, on certain peculiarities of constitution 

 conferred upon them at their birth; and as the longevity 

 of the one depends on a certain force of vitality, which, 

 after a period, grows weaker and weaker, so the duration of 

 the other may be governed by the quantity of prolific power 

 bestowed upon the species which, after a season, may decline 

 in energy, so that the fecundity and multiplication of indi- 

 viduals may be gradually lessened from century to century, 

 ^ until that fatal term arrives when the embryo, incapable 

 of extending and developing itself, abandons, almost at the 

 instant of its formation, the slender principle of life by 

 w^hich it was scarcely animated, — and so all dies with it.' "^ 

 In opposition to this doctrine, I contended that there is no 

 'reason to suspect that the last individuals" of a species of 

 which the numbers are diminishing is physiologically de- 

 teriorated, or is in the least degree impaired in its prolific 

 powers ; for there are known causes in the animate and in- 

 animate world which must in the course of ages annihilate 

 species, however vigorous 

 might remain. As the death of the last representatives of a 

 species would be abrupt, I conjectured that the birth of new 

 forms might be equally so, but as I had entire faith in the 

 doctrine that what is now going on in the natural world affords 



their powers of reproduction 



-» 



Brocelii, Couch. Eoss. Subap., tomo i. 1814 



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