vm WILD AND DOMESTIC VARIETIES 79 



egg ? There are many who plump for the egg ; 

 who see in the new form the manifestation of a new 

 kind of gamete in which, through some disturbance 

 in the normal process of division, a factor has been 

 omitted, or perhaps added. At some stage or other, 

 the normal equal distribution of the various factors 

 has been upset, whereby some of the gametes receive 

 a factor less or a factor more than the others. 

 From the union of two such gametes, provided they 

 are still capable of fertilisation, comes the zygote 

 which in course of growth develops the new character. 

 It may be that in some cases this is the sequence 

 of events, and that the egg precedes the owl. But 

 there are others which suggest that the owl came 

 first. 



One of the best pedigreed of all sports is the 

 "cretin" sweet-pea, a monstrous form so called from 

 its fancied resemblance to a gaping mouth with a 

 protruding tongue (cf Fig. 1 7). It appeared suddenly 

 in a large family belonging to a strain in. which 

 thousands of normal individuals had been accurately 

 recorded over a period of several years. From its 

 first appearance it behaved as a simple recessive to 

 the normal form, and has continued to do so ever since. 

 It had more than 200 normal sisters, of which none 

 that were tested threw any cretins. If the parent 

 plant had been producing an appreciable number of 

 " cretin "• gametes, we should have expected' an 

 appreciable proportion of the cretin's sisters to 

 have thrown cretins. And if the parent plant had 

 been producing very few such- gametes, it is almost 

 incredible that the only cretin egg to produce a 

 plant should have been fertilised by a cretin pollen 



