THE GENERIC TREE. . 181 



ent on simple causes ; for the law of all nature is from the 

 simple to the complex, rather than from the complex to the 

 simple. 



SUMMARY. 



The laws of breeding may be likened in their development 

 to a tree. First the root, then the trunk, branches, twigs 

 and leaves. The root represents law, — the law of causation, — 

 or, as it may perhaps be called, the law of unity, — the law 

 which directly preserves the harmony of all nature. This 

 primal law is the idea, which, as a conception and as a fact, 

 is the support of all processes of thought, whether of induc- 

 tion or deduction. The trunk stands for the conception 

 expressed by the term persistence of force (a law scarcely of 

 less universality than that of causation), because on it are 

 built up all the rest of the parts united with and flowing from 

 it. The limbs represent in turn subordinate and connected 

 laws, — such as those of resemblance and variation. The 

 twigs, other laws still more subordinate to the rest, — such as 

 find expression in the terms reversion, prepotency, etc. The 

 leaves can bring to mind the laws directly affecting the species 

 and the individual. 



We might use in illustration a figure calling attention to the 

 gradual succession and inter-dependent position of laws, whose 

 understanding constitutes the science of breeding, the whole 

 structure passing from the periphery of individual facts 

 through successive gradations of deductions, in which the 

 facts reappear in successive integers, until all observations 

 unite into a completed aggregate, and give conception of and 

 expression to the law founded in nature available for this 

 development or evolution. 



In our several divisions we have traced the law of persist- 

 ence of force, as well as regarded the law of unity, by con- 

 sidering in turn those parts and functions which take part in 

 the formation and evolution of the adult life. We have shown 

 that the germ and the sperm-cells have a development analog- 

 ically parallel, and that they are governed in their develop- 

 ment by the operation of the same laws. We have attempted 

 to show that, in generation, we have but an expression of the 

 same laws which operated to procure the elements essential 

 to it. That development and growth, the sequeke to genera- 



