EXPERIMENTS WITH ALCOHOL 129 



of the poisons on the germ plasm. It should be possible in an 

 experiment of this sort to see whether in Fi the usual condi- 

 tions as to Mendelip.n dominance are in any manner or degree 

 disturbed by the administration of the poisons to the parents. 

 Further, when the Fi individuals from treated parents are them- 

 selves bred there will be an opportunity to apply the most 

 delicate of all genetic tests for the composition of the germ 

 plasm, namely the test of segregation in F2 and succeeding 

 generations. 



A further possible advantage of the plan of having the 

 treated individuals belong to two distinct pure breeds, or races, 

 arises from the fact that advantage will then be taken of any 

 increase in physiological vigor, if any such occur, which arises 

 from the condition of heterozygosis (East and Hayes, 6). In 

 any breeding experiments of this sort it is highly desirable, 

 for purely practical reasons, to start at least with as high a 

 degree of general constitutional vigor in the animals as is pos- 

 sible, because it will make the getting of progeny in large num- 

 bers by so much the easier. 



There appears to the writer to be no disadvantages of any 

 weight which can be brought forward against the plan of using 

 two pure breeds and making the progeny cross-bred animals in 

 such an investigation as this, provided one is thoroughly ac- 

 quainted with the strains which he uses to start the experi- 

 ments. In the investigation here reported the foundation stock 

 used came from pedigreed strains of two breeds, Black Ham- 

 burgs and Barred Plymouth Rocks. Both of the strains used 

 have been so long pedigree-bred by the writer, and used in such 

 a variety of Mendelian experiments, that they may be regarded 

 as reagent strains, whose genetic behavior under ordinary cir- 

 cumstances may be predicted with a degree of probability 

 amounting practically to complete certainty. Furthermore the 

 results of crossing these two breeds reciprocall}" have been thor- 

 oughly studied by the writer. The large amount of material 

 which has accumulated in this laboratory, showing the genetic 

 behavior in a Mendelian sense of these two particular strains 

 when crossed together under normal circumstances may, to a 



THE JOURN'AL OF EXPERIMENTAL ZOOLOGY, VOL. 22, XO. 1 



