104 INHERITANCE 



white Fantail; and then paired the mongrel Barb- 

 Spot with the mongrel Barb-Fantail, the result being 

 that he obtained a family of birds which in colour 

 and markings were almost identical with the blue 

 Rock pigeon, the common ancestor of all domestic 

 pigeons. 



The tendency of cultivated and domesticated 

 plants and animals to revert to a former ancestral 

 condition may perhaps be illustrated mechanically 

 in this way. Take a pack of cards, and lay it on 

 the table ; the cards will all lie on their sides, and 

 be in a condition of stable equilibrium, so that the 

 table may be struck or shaken without materially 

 affecting their position : this represents the normal, 

 i.e., the wild or ancestral condition of the race. 

 Now arrange the cards on their edges, resting them 

 against one another, and so building them up into 

 a pagoda: the resulting structure is a far more 

 imposing one than the pack of cards when laid flat 

 on the table, but it is also an eminently unstable 

 one, its instability being directly proportional to 

 the extent to which it departs from the initial con- 

 dition : a very slight shake or push of the table 

 will cause the whole structure to collapse, and 

 revert to its condition of initial stability, the cards 

 all falling flat on their sides as at first. So 4:he 

 Pouter or the Fantail are much more impressive 

 and remarkable birds than the blue Rock, but the 

 former are artificial productions, in a condition of 

 great instability, and very readHy revert to the 

 ancestral condition. These are but a few of 

 the considerations which must be kept in 



