334 SPARKS FROM A GEOLOGIST'S HAMMER. 



close as in a human family; but they are of the same 

 kind, and they impress themselves on us in the same way 

 and with the same effect. We have not been accustomed 

 to thinking of the members of the cat-family as having 

 a common descent; but we universally recognize a close 

 relation of structure, form, movements and instincts. 

 Any one who should ask himself how resemblances of 

 structure, form, movements and instincts arise, would at 

 once perceive that they probably imply common ancestry. 

 It is conceivable that separate species so characterized 

 should have had separate origins; but our intelligence 

 inclines to the other explanation. The reason of this is 

 the fact that we are familiar with examples of more in- 

 timate family resemblance in cases of known consanguin- 

 ity. The children of John Smith are quite certain to re- 

 semble their parents, and may reproduce predominantly 

 traits of their grandparents or remoter progenitors. It is 

 not needful to suggest similar illustrations throughout 

 the animal and vegetable kingdoms. All our observation 

 and knowledge, therefore, point to consanguinity as the 

 cause of all family resemblances; and we have no knowl- 

 edge of any other cause of them. There is no ground of 

 hesitation to accept consanguinity as the true explanation, 

 save our preexisting assumption that all distinct specific 

 forms are independent originations; and if we scrutinize 

 this assumption, we perceive that it is held simply be- 

 cause it has been taught us in our childhood. That 

 opinion has been thought demanded by our intuition and 

 traditional belief concerning the relation of creator and 

 the world; but when it is shown that the demands of this 

 intuition and belief are better satisfied by the admission 

 of a consanguineous relation among animals, it would seem 



