Keactions and Peoducts in Interspecific Crosses 95 



orthogenetic modifications in the constitution of the gametes during the life of 

 the individual. In these forms there is no rhythm in the constitution of gametes 

 produced, and the germ-cells are identical in constitution and array at all por- 

 tions of the reproductive period, as far as I can determine. 



When crosses are made between the two species, in either direction, with 

 pedigreed, guarded parents, under conditions common to the two stocks, the 

 result in F^ is the uniform production of an intermediate type that is truly 

 intermediate in aU respects, as shown in figure 7, plate 8.^ When these 

 are inbred they uniformly produce F^ fraternities that in all instances show 

 complete segregation in the proportions of : diversa 1 : mid-type 2 : signati- 

 collis 1, in remarkably close approximations to the expected arrays, not infre- 

 quently in perfect proportions of 1:2:1. Both of the extracted forms are 

 distinctly cut off from the heterozygous type and are the entire type extracted, 

 and are not the separation of the elytral or other characters alone. The extracted 

 types when crossed back upon the parent stock show no indication of difference 

 in composition or in any other respect as the result of its passing through the 

 cross. The total type has remained as a unit in the gametogenesis of the F^ 

 heterozygotes, no interchange of characters taking place between the two sys- 

 tems, although there are many that might have done so, so that the Fj array 

 shows the two parent forms as unaltered extracted Fj types, and the mid-type, 

 which is heterozygous. 



The results obtained from the crossing of these two species under neutral 

 conditions, and also a complete testing of the crossing in all combinations, 

 everywhere and at all points in the series, show that the two types come out of 

 the cross with perfect regularity, unchanged, showing most constant and 

 regular behavior and retention of the integrity of the gametic systems through- 

 out. Each acts as a " single character " in the cross, and the entire series pre- 

 sents the aspect in operation, as in results, of a typical monohybrid reaction, 

 in which the contrasting elements are the two gametic systems present, one 

 from each species. In table 4 are given some of the results of the breeding of 

 these two species in this cross, and the working-out of the relations in Fg and Fj, 

 showing the uniformity in close approximation of the arrays to the theoretical 

 proportions of each type in the population. I have bred the heterozygous types 

 through to Fi2 without any change in the array presented or deformity in the 

 proportions. 



The extracted types in F, and following generations were always true to type 

 without exception. When crosses were made between the F^ heterozygotes and 

 either of the parent species — and the same is true of a heterozygote at any point 

 of any origin in the series — they give in F^ a 1:1 ratio of heterozygotes and 

 extractives of the same kind as the parent stock used. These, when bred out in 

 Fj, showed that the heterozygotes always gave a typical and close approximation 

 to the 1:2:1 Fg array, while th« extracted type came true in all. Identical 

 results came from the crossing of the extracted types and any of the heterozygous 

 individuals. Crosses between any of the extracted types and the natural species 

 gave, if of like types, uniform lines; if of unlike types, the characteristic F^ 

 heterozygotes and the Fg array seen in other crosses ; and likewise crosses between 



* Compare plate 8, figure 7 with parent species, L. signaticollis, plate 8, figure 9; 

 plate 1, figure 9. 



