| Femur and tibia | 81 | to | .89 |
| Femur and humerus | 84 | to | .87 |
| Humerus and radius | 74 | to | .84 |
| Humerus and ulna | 75 | to | .86 |
| Clavicle and humerus | 44 | to | .63 |
| Clavicle and scapula | 12 | to | .16 |
| Stature and femur | 80 | to | .81 |
| Stature and humerus | 77 | to | .81 |
| Stature and fore-arm | .37 | ||
| Stature and cephalic index | — | .80 | |
| Length and breadth of skull | 29 | to | .49 |
| Breadth and height of skull | 10 | to | .34 |
| Length and capacity of skull | 50 | to | .89 |
| Length x breadth x height and capacity of skull | 70 | to | .80 |
| Weight and length (babies) | 62 | to | .64 |
| Weight and stature (adolescents) | 50 | to | .72 |
| Right and left femur | .96 | ||
| Right and left first joint of ring finger | .93 | ||
| First joints of right hand, index and middle fingers | .90 | ||
| First joints of right hand, index and little fingers | .82 | ||
| Metacarpal phalanges, right hand, index and middle fingers | .94 | ||
| Metacarpal phalanges, right hand index and little fingers | .89 | ||
| Strength of pull and stature | 22 | to | .30 |
| Strength of pull and weight | 34 | to | .54 |
A study of this table shows us how justified was Darwin's contention that the evolution of one organ necessarily means the evolution of many parts of the body.
The modern methods of studying evolution have still another application. It is sometimes said that variation and heredity are the two factors of evolution. Heredity is, however, only a special case of correlated variation; a correlation between parents and offspring or between any two blood relatives. So evolution is reduced |to |a single factor—variation, simple and correlated.
|As a criticism of the new methods of studying variation it has been urged that, after all, they deal not so much with the causes of evolution as with the mere results. |to |this criticism it may be rejoined that the first step toward the determination of the causes of a phenomenon is a precise knowledge of the limitations and conditions of the phenomenon itself; and this is what the quantitative study of variation gives. Science has been more retarded by wasted efforts |to |explain erroneous data than by conscientious attempts |to |discover the precise facts. For when the facts are correctly known the true explanation often follows at once. Even if the explanation does not follow at once the proper direction of experimentation |to |discover causes is indicated. Statistics tell us not only the exact static condition of species to-day under the varying circumstances of environment; but they will enable us |to |measure precisely the results of any change in environment, artificially or naturally brought about. We
