266 EdmundB. Wilson: 
quantitative difference of metabolism. I was thus led to suggest 
(1905, 1906), "that the same kind of activity that produces a 
male will, if re-enforced or intensified, produce a female“. More 
recently, "There is a certain temptation in the thought that the 
+0 
Se 
x): 
Q 
D 
Q 
a 
we 
ee 
Age Gr) 
> 
| 
ae 
I) 
uk 
2 
or 
sexual differentiation may be rooted in a simple principle of plus 
and minus that holds true of all sexual organisms, from the 
lowest to the highest, and may be an expression of a fundamental 
principle of metabolism“ (1910c). The same principle has been 
adopted by Boveri (1909) and by Goldschmidt (1910). 
Already in 1904. (before the relation of the sex-chromosomes to 
sex-production had been determined) the last-named author 
suggested that the X-chromosome might be a special store-house 
