336 Action of the Genetic Material 



termination, meaning that the sex detenniners of one sex are located 

 in the X-chromosomes, those of the other sex outside, and that the 

 quantities of two in the X-chromosomes win out over the action of the 

 ever constant determiners of the other sex, while one quantity does 

 not succeed in doing so: in Lymantria, F > M < MM; in Drosophila, 

 MM > F < FF. 



In Lymantria it seemed possible to link dosages with genie action 

 when it was found that F and M, at that time considered to be sex 

 genes, existed in different states or potencies, called strong and weak. 

 That is, the combination of a strong F with two weak M's made the 

 genetic males intersexual in spite of a normal chromosome comple- 

 ment; and, vice versa, a weak F with one strong M made females inter- 

 sexual. All grades of these potencies could be found, and their combi- 

 nations always gave the predictable result: we know that F/MM is 

 a male, but if Fs is a very strong F and Mw a very weak M, the com- 

 bination Fg/MwMw results in a sex-reversal female. If M^j-Mwj are 

 increasing grades of strength of M, Mwj being identical with a strong 

 M, or Mg, it is possible to replace in the Fs/M^Mw individuals one of 

 the M's by Mwi or Mwj, and so on to M^s- The result is, with the 

 exactness of a set of equations, that Fg/MwMwi is a high-grade male 

 intersex; Fg/MwMwjj a less extreme male intersex; Fg/Mw-Mwj, a 

 medium one; and so on until Fg/MwMwg is a normal male. (See 

 Goldschmidt, 1930; and fig. 23, below.) As this series — and all other 

 comparable experiments which gave completely consistent results — 

 merges at both ends of the different M potencies into the normal 

 dosage relation F/MM = S F/M = 9 (F>M<MM), the conclu- 

 sion was obvious that the potencies of F and M are also dosages, 

 different quantities of the sex determiners F and M. As we stated in 

 another connection (see I 2 C d ee), today it is certain that F in 

 Lymantria is inherited in the Y-chromosome, and that M in the 

 X-chromosome probably is represented by a set of heterochromatic 

 sections. The quantity of M would then be the quantity of this hetero- 

 chromatin, which agrees with the facts reported previously that quan- 

 tities of extra-heterochromatin may have corresponding effects in shift- 

 ing phenotypical features (e.g., variegation). Thus we would still deal 

 with dosages, though not doses of "genes." 



In the old Lymantria work, the facts of intersexuahty permitted 

 establishing what was considered to be a kinetic relation between 

 dosage and effect. In intersexes, development proceeds first according 

 to the chromosomal sex (1X-2X), which probably means, as we 

 saw before when discussing cytoplasmic conditioning, that primary 



