Chap. XXIII. CONDITIONS OF LIFE. 285 



characteristic features of certain allied species, or even genera. Suppose 

 says Eeissek, "the condition originally caused by the fungus to become 

 " constant in the course of time, the plant would, if found growing wild 

 " be considered as a distinct species or even as belonging to a new genus " 

 I quote this remark to show how profoundly, yet in how natural a manner 

 this plant must have been modified by the parasitic fungus. 



Facts and Considerations opposed to the belief that the Conditions 

 of Life act in a potent manner in causing definite Modifications 

 of Structure. 



I have alluded to the slight differences in species when 

 naturally living in distinct countries under different conditions ■ 

 and such differences we feel at first inclined, probably to a 

 limited extent with justice, to attribute to the definite action 

 of the surrounding conditions. But it must be borne in mind 

 that there are a far greater number of animals and plants which 

 range widely and have been exposed to great diversities of 

 conditions, yet remain nearly uniform in character. Some 

 authors, as previously remarked, account for the varieties of our 

 culinary and agricultural plants by the definite action of the con- 

 ditions to which they have been exposed in the different parts 

 of Great Britain; but there are about 200 plants 55 which are 

 found in every single English county ; these plants must have 

 been exposed for an immense period to considerable differences 

 of climate and soil, yet do not differ. So, again, some birds, 

 insects, other animals, and plants range over large portions of 

 the world, yet retain the same character. 



Notwithstanding the facts previously given on the occurrence of highly 

 peculiar local diseases and on the strange modifications of structure in 

 plants caused by the inoculated poison of insects, and other analogous 

 cases; still there are a multitude of variations— such as the modified skull 

 of the mata ox and bulldog, the long horns of Caffre cattle, the conjoined 

 toes of the solid-hoofed swine, the immense crest and protuberant skull of 

 Polish fowls, the crop of the pouter-pigeon, and a host of other such cases 

 —which we can hardly attribute to the definite action, in the sense before 

 specified, of the external conditions of life. No doubt in every case there 

 must have been some exciting cause; but as we see innumerable indivi- 

 duals exposed to nearly the same conditions, and one alone is affected, we 

 may conclude that the constitution of the individual is of far higher 



55 Hewett C. Watson, ' Cybcle Britannica/ vol. i., 1847, p. 11. 



