372 



THE AMEBIC AK NATURALIST [Vol. LI 



over individual in which gone G is held incorporated by force 

 Fg with the converse crossover individual in which gene g is 

 held incorporated by force (see diagram, line 3). As soon 

 as the chiomosomes of the resulting heterozygote enter the proper 

 resting stage the forces F^ and Fg relax, freeing the genes G 

 and g. It must now be recalled that every value of force Fo is 

 a member of a specific frequency distribution representing the 

 entire behavior of F^,, and that any particular value of force Fq 

 should give in succeeding generations the same result as every 

 other value of F^. Each value of Fq, whether chosen from the 

 extreme upper range, the extreme lower range, or the mid-region, 

 should give rise among its descendent cells to a series of variates 

 which reproduce the original distribution F^ and no other. 

 That is, the two distributions which describe the variates of Fq 

 and of Fg in the cells of the new heterozygote, being specific, 

 overlap in exactly the same fashion and to the same extent as did 

 the distributions of the forces F^ and Fg in the original hetero- 

 zygote (see diagram, line 3). Consequently, when the chromo- 

 somes are reassembled force F^ will as before, incorporate gene 

 G in 99 per cent, of cases and gene g in 1 per cent, of cases (see 

 diagram, line 4). Bui gene G entered the heterozygote as part 

 of the chromosomf />o.s.sv.«;//ry force F,„ hence the 99 per cent, of 

 emerging offsprhi*/ !,> which gnu G /.s- hu'orporaff<l hg the chro- 

 mosome hearing or gnu <j h,, fh> rhromusomt hearing are 



crossovers are of the same frequency as in the original exper- 

 iment. The intensities of coupling and of repulsion are equal 

 and not complementary. Goldschmidt's machine which at the 

 first revolution turned out a mere driblet of crossovers, should 

 overwhelm the operator with a deluge of crossovers at the next 

 turn of the crank. The whole explanation fails unless some added 

 agency be devised to take over the duty which the specific allelo- 

 morphic forces abandon after the occurrence of crossing over. 



The original problem was to secure the replacement of gene 

 G in chromosome C by gene g, and at the same time the replace- 

 ment of gene g in chromosome C by gene G. Having assumed 

 the machinery of specific variable forces to accomplish this inter- 

 change, we find that the products of the interchange are not 

 stable, and furthermore they give a result the opposite of that 

 demanded by the well known facts of linkage. In order that 



