138 



THE AMERICAN NATURALIST [Vol. XLV 



of these experiments lias been attacked on the ground 

 that the Parameciums multiply asexually; but this mat- 

 ter seems to me of no importance in the present case. 

 The experience that pure-line breeding of plants and 

 pure-strain cultures of micro-organisms, in full agree- 

 ment, demonstrate the non-adequacy of selection as a 

 genotype-shifting factor, is a circumstance of the great- 

 est interest. Also Woltereck's experiments with 

 Daphnias, the important researches of Wolff, and the 

 highly interesting indications of C. 0. Jensen as to 

 bacteria may be mentioned here as further supports for 

 this view. Quite recently Pearl has arrived at the same 

 conclusion as to the egg-production by fowls. 



The famous Galtonian law of regression and its corol- 

 laries elaborated by Pearson pretended to have estab- 

 lished the laws of "ancestral influences " in mathemat- 

 ical terms. Now, by the pure-line explanation of the 

 well known action of selection in poly-genotypic popu- 

 lations, these laws of correlation have been put in their 

 right place; such interesting products of mathematical 

 genius may be social statistics in optima forma, but they 

 have nothing at all to do witli genetics or general biol- 

 ogy! Their premises are inadequate for insight into the 

 nature of heredity. 



Ancestral influence! As to heredity, it is a mystical 

 expression for a fiction. The ancestral influences are 

 the * 'ghosts'' in genetics, but generally the belief in 

 ghosts is still powerful. In pure lines no influence of the 

 special ancestry can be traced; all series of progeny 

 keep the genotype unchanged through long generations. 

 A. D. Darbishire's laborious investigations as to the 

 classical object of Mendel's researches, green and yellow 

 peas, may even convince a bionietrician that the ances- 

 tral influence is zero in "alternative inheritance." An- 

 cestral influence in heredity is, plainly speaking, a term 

 of the "transmission-conception" and nothing else. 

 The characters of ancestors as well as of descendants 

 are both in quite the same manner reactions of the geno- 



