339 
On THE CHANGE THAT TAKES PLACE IN THE CHROMO- 
SOME IN MuTATING STOCKS. 
Roscor R. Hyper. 
Two new eye mutations, tinged and blood have appeared in my 
cultures of the fruit fly that throw light upon the question as to the nature 
of the change that takes place in the chromosome when a new character 
appears. Both mutations show typical sex-linked inheritance, consequently 
they are expressions of changes in the X chromosome. Both mutants give 
the same linkage values when measured with other sex-linked characters. 
When measured with yellow body color a linkage of 1.2 results; with minia- 
ture wings 33; with bar eyes 44. Morgan has deseribed three sex-linked 
eye mutants, white, eosin and cherry, which give the same linkage values. 
Consequently, we now have five sex-linked eye mutants, namely, white, 
tinged, eosin, cherry and blood, which give an increasing color series from 
white to the bright red of the wild fly. A study of their linkage relations 
shows that they either lie very closely together on the X chromosome or that 
they are but different modifications of the same gene. The two possibilities 
involve the question of the origin of mutations as well as the fundamental 
make-up of an hereditary factor. 
Mendel evidently thought of something in the germ cell that stood for 
round (R) and something that stood for wrinkled (W) and that these two 
things could not coexist in the same gamete. That is, (W) isallelomorphic 
to (R). 
The origin of mutation in the light of the above assumption would 
seem to depend upon the splitting up of more complex hybrids—the bring- 
ing to the surface of units already created. Kvolution in the light of such 
a conception would seem to depend upon the shifting together of desir- 
able units. 
Bateson viewed the matter in a different light. He knew of the origin 
of new forms by mutation. He postulated a definite something in the germ 
cell that stands for the character, as for example (T) which stands for the 
tallness in peas, which when lacking makes the pea a dwarf (t). In other 
words, instead of two separate factors he regards the tallness and dwarfish- 
ness merely as an expression of the two possible states of the same factor,— 
