282 P^of. Guthrie, LL.B. — -On the Subjective Causes ©/"[April 25, 



" Only give us sufficient time," the casual evolutionist would say, 

 " and without requiring any law by which organic variations are 

 harmoniously correlated we can account for the fact that in the 

 outcome they are and must be so related." This is true, but the 

 demand for time becomes excessive. 



The correlation of variation of which w^e are now treating is 

 however something more than this. It is the law by which without 

 reference to natural selection, or the advantage of the individual, one 

 part of an organism cannot "vary without involving the variation 

 of other parts also. 



This subject has been so fully treated by Darwin that it is hardly 

 necessary to do more than to refer to his works on this subject. 



Darwin has shewn that as both animal and vegetable forms, even 

 those most highly developed, consist to great extent of variously 

 developed homologous parts their parts must tend to vary corre- 

 latively to each other. Thus, for example, the jaws are related 

 to one of the three modified vertebrae, constituting the skull, in the 

 same way as the fore limbs are to another of these vertebrae and 

 the hind-limbs to one of the sacral vertebrae. Now Darwin points 

 out how breeders have noticed that these parts vary together, so 

 that elongated jaws are generally found with elongated limbs, both 

 fore and hind. Not only however do homologous parts vary together, 

 but the same is the case with respect to parts between which there 

 is no apparent homology, as in the oft-quoted case of white blue- 

 eyed cats being nearly always deaf, and tortoiseshell cats of the 

 female sex. 



Again flowers and fruits are modified leaves. The varieties of 

 cultivated fruits have been produced by man's selection with reference 

 to the fruit itself. Yet an experienced horticulturist can distinguish 

 the different varieties from the correlated and unintentional variations 

 of the foliage. 



How far-reaching is this correlation of parts is w^ell illustrated 

 hy the fact that the experienced hologist can reconstruct the entire 

 animal from the fragment of a bone, can tell you not only that it 

 is a bird and not a mammal or reptile, but can tell you to w^hat tribe 

 of birds it belongs, what was its size and its habits. So from a few^ 

 grains of tenui carbonized wood the phylologist will reconstruct 

 a tree with foliage, flower and fruit. 



(2.) The existence of a tendency to vary in certain directions with a 

 -capacity of varying in others is well illustrated from the experience of 

 breeders of plants and animals. 



