4 86 POPULAR SCIENCE MONTHLY. 



shot in its career. In rare cases a long run of luck continues to 

 favor the course of a particular shot toward either outside place, 

 but in the large majority of instances the number of accidents 

 that cause deviation to the right balance in a greater or less 

 degree those that cause deviation to the left. Therefore most of 

 the shot finds its way into the compartments that are situated 

 near to a perpendicular line drawn from the outlet of the funnel, 

 and the frequency with which shots stray to different distances 

 to the right and left of that line diminishes in a much faster ratio 

 than these distances increase. 



Types which are based upon vital statistics have peculiar in- 

 terest, since they persist from generation to generation, according 

 to what is known as the law of specific stability, while they also 

 undergo slow chauges according to the principle of the mutability 

 of species. 



Individuals come and go, but the type persists, and its slow 

 changes may be pictured as quite independent of and more sub- 

 stantial than the procession of individuals which files past only 

 to vanish from the world. 



The statistical comparison of vital types affords a means for 

 studying the phenomena of inheritance by the exact methods of 

 mathematics, and it is capable of yielding definite and valuable 

 results, so far as the vital phenomena which are studied can be 

 treated as if they stood alone, but the attempt to generalize from 

 vital statistics and to deduce general laws of inheritance from 

 them is attended by peculiar difficulties, due in great part to the 

 fact that the data which are studied are not separable from the 

 organism wjiich exhibits them. Stature or size or weight may 

 be treated abstractly for statistical purposes, but the stature of 

 an organism is not an abstraction, for the organism is not only a 

 bundle of properties, but a unit as well, and its stature is only one 

 among many features which are all beautifully co-ordinated with 

 each other in such a way as to promote the welfare of the species. 

 A generalization which ignores this fact and treats stature as an 

 abstraction may, while proved by statistics, be untrustworthy as 

 a contribution to our knowledge of inheritance. 



In popular language, specific stability may be said to be due to 

 inheritance, and specific mutability to variation ; but in this con- 

 nection these words have only a loose meaning. In so far as they 

 convey the impression that the stability of species and the muta- 

 bility of species are antagonistic to each other, or are due to two 

 distinct and opposing influences, these terms are unfortunate, for 

 we have good ground for holding that they are due to the same 

 influence the extermination of certain individual peculiarities, 

 and the preservation of others by natural selection. 



The older naturalists held that adherence to type is due to 



