186 BOARD OF AGRICULTURE. 



under law, in which the past forces are continually in action, 

 and a given result can only occur through predetermined 

 forces in the past. Hence an order to development. Hence 

 the element of time, during which changes may occur in suc- 

 cession preparatory to the final result. Hence, in embry- 

 ology and immature growth, a guide for the study of the 

 history of past changes or evolution. 



Correlated variations, as of homologous parts, and correla- 

 tions in general, can be understood under this view of forces, 

 continuously modifj-ing and influencing each other. When 

 the phenomena of life first appeared, the struggle for exist- 

 ence commenced, and in meeting the requisite equilibrium, 

 changes became impressed in relation with the complexity of 

 environmental forces, differentiations occurred, and the animal 

 was gradually built up in its wondrous intricacy, yet har- 

 mony ; each force concerned acting on, and being acted upon, 

 by other forces concerned. Where we recognize this action 

 of one force (considered concrete in its results) upon another 

 (considered likewise), we define the action as correlation. 

 Thus, in all the breeds of the pigeon, the length of the beak 

 and the size of the feet are correlated. All modifications 

 which occur influence subsequent developments, not only of 

 the same parts, but also of all other parts with which it is 

 intimately enough connected. In this we have correlated 

 variations, in this but an expression of results following the 

 doctrine of the indestructibility of force, which teaches that 

 force, in common with matter, cannot be created, but can only 

 be converted, and is subject to changes, but never to loss. 

 In the correlations between bone and hair, we have different 

 structures built up in part from the action of the same forces, 

 as is shown by the history of their development. We there- 

 fore have a certain affinity between them, and a change 

 impressed on one is apt to be followed by corresponding 

 changes in the other. Were we sufficiently acquainted with 

 the forces which go towards making up the animal, the 

 numerous immediate forces could be referred to successive 

 intermediate forces, into which they could be grouped, until 

 finally the simple force would be reached, — a conception 

 expressed by vitality in the abstract. Correlation is, conse- 

 quently, but another expression of persistence of force. It 



