THE MUTATED OENE 



31 



indicates that up to this time the cephalic complex was measured, 

 and later the eye disk alone. The actual differences are then 

 determined very early in development. Unfortunately, oothing 

 at all is known a- to how these differences originate whether 

 fewer cell <li\ isions take place or an .1 nlagi of normal sizeissecond- 



1000 

 900 

 800 

 700 

 600 

 500 

 400 



300 



200 



100 



40 



zo 



24 36 4d 60 72 84 96 

 Pupae 

 Fig. 13. The logarithmic growth curves of the imagina] eye disks of Wild t >j .«• . 

 glass, eyeless, and Lobe larvae (between 36 and 48 hr. the cephalic complex 

 separates the eye <lisk propel - From Medvedev, 1936, /.. tad. Abstl. 70, Fig. 3.) 



arily reduced. Thus at present the only conclusion to l>e drawn 

 i- that genes are involved which control early processes of 

 differentiation. It seems thai the story is a differenl one for 

 the Bar-eye mutants of Drosophila. According to Chen, the 

 youngesl stages of the Bar eye have the same aze as those of the 

 Full eye, and only later do the size differences appear. No details 

 are yet known; hut certain experimental fad page 76) 



