No. 531] GENOTYPE CONCEPTION OF HEREDITY 141 



termined abnormalities which show the normal form of 

 heredity through both ovum and sperm. The case quoted 

 demands further experience and seems not to be in ac- 

 cord with results of Baur's experiments. At any rate, 

 there may be several difficulties to overcome in the full 

 and consistent application of the genotype-conception, 

 difficulties that may be characterized as perturbations 

 by infection or contamination. And hereby it must be 

 remembered that theoretically, as well as practically, 

 there are no sharp limits between "normal" and "path- 

 ological" manifestations of life. "Nature is beautiful, 

 but not correct," is a Danish saying. 



The principle of pure lines or, generally, pure culture, 

 is of importance also for elucidating the celebrated ques- 

 tion of the inheritance of "acquired characters." Men- 

 delism and pure-line researches are here in the most 

 beautiful accordance, both emphasizing the stability of 

 genotypical constitution ; the former operating with the 

 constituent unities, the latter with the behavior of the 

 totality of the genotypes in question. The brilliant work 

 of Tower with Leptinotarsa and the highly suggestive 

 injection experiments of MacDougal indicate that 

 changes of the genotypical constitution are produced by 

 steps, discontinuously. And as yet no experiment with 

 genotypically homogeneous cultures has given any evi- 

 dence for the Lamarckian view, the most extreme 

 "transmission "-conception ever issued. As to bacteria, 

 the important experiments recently made by C. 0. Jen- 

 sen for the purpose of changing their types through 

 adaptation have given not only absolutely negative re- 

 sults, but have demonstrated the fallacy of some posi- 

 tive indications by previous authors. Lamarckism and 

 selectionism are certainly at bottom the same thing: the 

 belief in personal qualities being "transmitted" to the 

 offspring. Observations in impure populations are now 

 their places of resort; nevertheless, it is granted that 

 their history in biology as suggestive ideas has been most 

 glorious. 



Apropos, some cases of apparent action of selection 



