136 THE THEORY OF MUTATION 



generations. The net result of his experiments was 

 this : out of about 50,000 individuals which were grown 

 to a recognisable stage, more than 800 showed muta- 

 tion that is to say, they differed specifically from 

 the parent 0. Lamarkiana. The 800 individuals 

 belonged to about fifteen new kinds, most of which 

 appeared repeatedly, though some were more frequent 

 than others. The process of mutation had, therefore, 

 taken place in about i per cent, of the seedlings which 

 were grown, and owing to various reasons this estimate 

 is probably considerably too low. For example, many 

 of the new forms were very weakly, and often died 

 before it was possible to distinguish them. Others, 

 again, could not be recognised until an advanced stage 

 of their growth had been reached, whereas only a small 

 proportion of the seedlings raised could be grown after 

 they had reached any considerable size, owing to con- 

 siderations of space. 



We cannot now follow de Vries veiy far into his 

 elaborate account of his new species and of the way 

 in which they originated ; a few general remarks only 

 must suffice. Many of the new forms were recognis- 

 able as quite young seedlings, notably 0. albida, 

 others not until a much later peiiod of their growth. 

 0. gigas was the finest and strongest of the new forms, 

 but only made its appearance on two occasions. 

 0. lata also appeared to be as strong as the parental 

 type, whilst two other forms were able to survive in 

 nature in competition with the original species, as 

 has been already described. Other forms which were 

 grown and flowered were plainly less well fitted for 



