VIII WILD AND DOMESTIC VARIETIKS 79 



egg ? There arc many wlio plum[) for tlic egg ; 

 wh(; sec in the new form the manifestation of a new 

 kind of gamete in which, through some disturbance 

 in the normal process of di\ision, 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. 

 F'rom the union of two such gametes, provided the)- 

 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. Hut 

 there are others which sucrirest 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 ga[)ing mouth with a 

 protruding tongue (cf Fig. i 7). It appeared suddenl\- 

 in a large family belonging to a strain in which 

 thousands of normal indi\iduals had been accuratcl}' 

 recorded over a period of several \'ears. From its 

 first a[)pcarance it beha\ed as a simple recessive to 

 the normal form, and has continued to do so e\cr since. 

 It had more than 200 normal sisters, of which none 

 that were tested threw an)' cretins. If the [parent 

 plant had been producing an appreciable number of 

 ''cretin" gametes, we should have expected an 

 ai)preciable proportion of tlie cretin's sisters to 

 ha\e thrown cretins. Aiul if the parent plant had 

 been jnoducing \cr\' few such gametes, it is alnuist 

 incredible that the only cretin egg to produce a 

 plant should have been fertilised b>' a cretin pollen 



