218 GENETICS IN RELATION TO AGRICULTURE 
be conceived to result in the production of male intersexes, 1.e., individuals 
of the chromosome constitution ZZ which display female characters, 
because the weaker potency simply means a more or less close approach 
to the potency of the normal factor in the heterozygous condition and a 
consequent approach of the individual to the characters of the male. 
Goldschmidt’s results are intensely interesting and promise much for 
an elucidation of the problems connected with sex-determination. 
We cannot refrain from drawing a comparison between these re- 
sults and some which have been secured in species crosses in Nicotiana. 
Thus a definite factor for calycine flower in Nicotiana tabacum causes the 
flowers to develop a petaloid calyx and a split corolla, a striking terato- 
logical form. The character is a simple recessive to the normal form in 
variety crosses but when crossed with N. sylvestris, a different species, 
the normal flower factor in N. sylvestris appears to possess a lower 
potency than that of normal flowered varieties of N. tabacum. Con- 
sequently the hybrids are intermediate with respect to the flower char- 
acter expression, all of the flowers on a given plant exhibiting some 
development of the calycine flower character. We interpret this to 
indicate that the normal flower factor of N. sylvestris does not interact 
normally with the set of factors which interact to determine the floral 
character expression in the hybrid, but that the calycine flower factor 
is able to interact normally and to its full extent with these factors. Asa 
consequence the flowers of the Ff; hybrid are strongly calycine. This 
interpretation is further supported by the fact which we have previously 
set forth in some detail that practically the entire set of characters are 
determined by the N. tabacum parent. It is conceivable that crosses 
with other species would show the same character of variability in po- 
tency as has been found for the sex-factors of Lymantria. At any rate 
a close analogy here exists between the behavior of sex as a character 
and the behavior of a character known to depend upon a simple factor 
difference. 
The evidence which has been presented with reference to the determi- 
nation of sex lends strong support throughout to the idea that sex-de- 
termination depends on the genotypic constitution of the individual. 
This does not, it must be clearly understood, mean that other external 
factors may not act to disturb the usual relations just as they occasion- 
ally do with other factors; but as in such cases these external factors 
must act in conjunction with the genotypic sex-factors. To assume 
that changes occur willy-nilly in the case of sex-factors is no more warrant- 
able than to assume that other factors change frequently in response to 
environmental conditions, an assumption that does violence to the high 
degree of stability which has been observed to obtain for factors in general. 
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