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Review of Darwin's Theory on the Origin of Species. 165 
ot Codlin-apple, could ever have proceeded from the seeds of the same 
tree, Innumerable other examples could be given. The explanation, I 
think, is simple: from long-continued study they are strongly impressed 
with the diiferences between the several races; and though they well 
know that each race variegslightly, for they win their prizes by selecting 
such slight differences, yet they ignore all general arguments, and refuse 
tosum upin their minds slight differences accumulated during many 
stiecessive generations. May not those naturalists who, knowing far less 
of the laws of inheritance than does the breeder, and knowing no more 
than he does of the intermediate links in the long lines of descent, yet 
admit that many of our domestic races have descended from the same 
parents—may they not learn a lesson of caution, when they deride the 
dea se ‘Species in a state of nature being lineal descendants of other 
species { 
The actual causes of variation are unknown. Mr. Darwin 
fayors the opinion of the late Mr. Knight, the great philosopher 
of horticulture, that variability under domestication 1s somehow 
connected with excess of food. He also regards the unknown 
Callse as acting chiefly upon the reproductive system of the pa- 
tents, which system, judging from the effect of confinement or 
cultivation upon its functions, he concludes to be more suscepti- 
ble than any other to the action of changed conditions of life. 
¢ tendency to vary certainly appears to be much stronger un- 
t domestication than in free nature. But we are not sure that 
greater variableness of cultivated races is not mainly owing 
to the far greater opportunities for manifestation and accumula- 
Yon—a view seemingly all the more favorable to Mr. Darwin’s 
- The actual amount of certain changes, such as size 
or abundance of fruit, size of udder, stands of course in obvious 
telation to supply of food. 
§ y, We no more know the reason why the progeny occa- 
Onally deviates from the parent than we do why it usually re- 
Sembles it, Though the laws and conditions governing varia- 
2 i may be accounted for, while the great primary law of inher- 
7p ehetine a mysterious fact. ; 
this ; common proposition is, that species reproduce their like ; 
thy eee of general inference, only a degree closer to fact 
the statement that genera reproduce their like. The true 
Proposition, the fact incapable of farther analysis is, that individ- 
