132 Heredity. 



other breeds, the chickens often have five toes on one 

 foot and four on the other. 



When the red flowered stock of Antirrhinum is fei'ti- 

 lized with the pollen of the pnrple Queen stock, about 

 half the seedlings resemble the mother plant, while the 

 other half bear rich purple blossoms like those of the 

 paternal plant. 



Darwin says that he fertilized the pnrple sw^eet-pea, 

 which has a dark reddish-pnrple standard-petal and vio- 

 let-colored wings and keel, with pollen of the painted- 

 lady sweet-pea, which has a pale cherry-colored standard 

 and almost white wings and keel, and from the same 

 jDod twice raised plants resembling both sorts, the greater 

 number resembling the father. 



These cases are difficnlt to explain, bnt the phenomena 

 are so complicated that it is hardly safe to specnlate 

 upon them nntil they are re-examined by an observer who 

 can devote himself to this snbject especially. 



Some of them may be due to the causes above indi- 

 cated, and some, possibly, to fertilization by two fathers. 



Crossing as a Cause of Reversion. 



Accordino- to Darwin's view reversion must in all cases 

 be due to the manifestation of a tendency Avhich has lain 

 dormant in the egg and has been transmitted for gener- 

 ations in a latent condition, for the chances against the 

 repetition, by an accidental variation, of a characteristic 

 of a remote ancestor, are inconceivably great. 



According to our theory this is not the case, for the 

 conditions which caused a cell in the ancestral form to 

 throw off gemmules and thus to produce a given pecu- 

 liarity may cause the corresponding cell of the parent to 

 throw off gemmules in the same way, and these, uniting 

 with the corresponding part of the egg, will produce 



