62 HEREDITY 



how long this radically important work of an Austrian 

 abbot in the distant 'sixties would have remained 

 in obscurity had not De Vries possessed the patience 

 and industry to look into it, the insight to recog- 

 nise, and the ability to demonstrate, its importance. 



Make Mendel's discovery simple I cannot, the facts 

 being complex ; but I must do my best. We have 

 seen that each gamete — of either sex — is formed by 

 a series of divisions beginning in a germ-mother- 

 cell. Now the essence of Mendel's discovery is this. 

 The germ-mother-cell, which is about to divide and 

 form the gametes that are to reproduce any indi- 

 vidual in his or her descendants, contains characters 

 derived from both the parents of that individual. 

 These characters exist in the germ-mother-cell in 

 opposed pairs — e.g. a character corresponding to the 

 white pigmentation of the individual's father, and a 

 character corresponding to the black pigmentation of 

 the mother. When the germ-mother-cell divides so 

 as to form the gametes, these opposed pairs of char- 

 acters are split up or segregated, the black character 

 going to one gamete and the white character to an- 

 other. Thus the gametes, or sex-cells, of a grey in- 

 dividual are not potentially grey, but either black or 

 white. The germ -mother-cell was grey (so to speak) 

 like the individual, but its greyness depended on the 

 possession of an opposed pair of characters, black and 

 white; and these characters are segregated during 

 gametogenesis. Observe now the result. The in- 

 dividuals of the new generation may be of three 

 kinds in respect of the character of colour. Some 

 of them will be white, since they are formed by the 



