Heredity in Population and in Pure Lines. 9 



sidered his maternal sweet pea seed as the "parents" and was 

 apparently of the opinion that a selection of extreme size of 

 mother seeds would bring about a change in the offspring con- 

 sonant with the selection. Johannsen in following the same plan 

 has perhaps fallen into an error and this has been noticed by 

 Weldon and Pearson. * If individual plants had been chosen for 

 parents and had the characters been taken from the means of 

 the seed of such entire plants selected, then a more logical 

 starting point would have been secured. This would have en- 

 tailed the growing of another generation. Our author certainlv 

 did not show that the extremes of seed in one plant have no ap- 

 preciable effect upon the similar qualities of the offspring seed. 

 It seems that he laid too much emphasis upon his showing that 

 the selection of fluctuations had no hereditary value when these 

 fluctuations were empodied in one plant. 



Johannsen recognized very well that chance must largely 

 govern the size of seeds upon one plant. The end bean in a pod 

 is, of course, smaller than the middle bean. But in spite of 

 this knowledge, he uses the different sizes of seed from one plant 

 as a basis of selection. We may easily conceive that the seeds of 

 one plant may vary germinally as well as somatically. Then if 

 seeds having germinal variations were selected, such variations 

 would appear in the offspring. The somatic or partial varia- 

 tions are considered by everyone to be only transient. To get 

 up an argument over them is too much like setting up a man of 

 straw. As Johannsen has treated the problem, the partial 

 variations mask the germinal ones. No basis is afforded for the 

 measurement of the various parents within the pure lines. 

 Strictly speaking, there are no different parents for the various 

 sub-lines. To secure such parents another generation would have 

 been necessary. It seems, then, that Johannsen has not demon- 

 strated the futility of selection within the line. He did not show 

 that the seeds of one plant obey Quetelet's law, which of course 

 was well known. 



Plate** criticizes Johannsen's work by stating that the self- 

 pollinated pean plants have become less variable than organisms 



*Biom. II, 499. 



**Archiv. f. Rassen-u. Gesel-Biol., I, 136. 



