 " When I recollect the fact that [ from ] the form of the body , shape of scales and general size , the Spaniards can at once pronounce from which island any tortoise may have been brought ; when I see these islands in sight of each other and possessed of but a scanty stock of animals , tenanted by these birds , but slightly differing in structure and filling the same place in nature ; I must suspect they are only varieties ... If there is the slightest foundation for these remarks , the zoology of archipelagos will be well worth examining ; for such facts would undermine the stability of species . " 
