ZOOGENESIS 



examples are the pugs, the Japanese pugs, the bull- 

 dogs, the Niata cattle of Argentina, short-faced pigs, 

 etc. A bull-dog skull has been found in an ancient 

 Inca grave in Peru, indicating that the bull-dog type 

 arose independently in America. 



"Bull-dog" cod, carp, chub, minnows, mullet, 

 pike, salmon and trout have been described. In the 

 case of carp and trout the "bull-dog" variety is very 

 common in certain limited areas. "Bull-dog" forms 

 of other vertebrates have also been recorded. 



A very interesting case of discontinuity is furnished 

 by the peach and nectarine. Darwin wrote that we 

 have excellent evidence of peach stones producing 

 nectarine trees, and of nectarine stones producing 

 peach trees. We see the same tree bearing both 

 peaches and nectarines. We find peach trees through 

 bud variation suddenly producing nectarines, the seeds 

 of which reproduce nectarines, as well as fruit which 

 is in part nectarine and in part peach. Finally, we 

 have a case of a nectarine tree first bearing half and 

 half fruit and subsequently true peaches. 



The variation from peach to nectarine or from 

 nectarine to peach may be total. If it is less than 

 total the fruit may be divided into either halves or 

 quarters so that for each segment the variation is still 

 total. There is no evidence of intermediate forms 

 other than these divided fruits. 



Bateson remarked that it is therefore a fair presump- 

 tion that intermediate forms are either rare or non- 

 existent, and that the peach state and the nectarine 

 state are thus positions of organic stability between 



[M7] 



