THE MUTATED GENE 243 



Thus, the main features of the future pattern become visible 

 in the form of a relief of protruding and of flattened scales. 

 Figure 49 shows such a stage from an intersexual wing, the later 

 male parts being represented by the valleys of the relief. Figure 

 50 shows a similar condition in the wing of a swallowtail butterfly, 

 compared with the finished pattern; and Fig. 51, a similar stage 

 in the formation of the eyespot in a Saturnid moth. This 

 differential velocity of differentiation within different parts of the 

 pattern was found in numerous different objects from diversified 

 groups, 1 including also the zigzag bands of Lymantria. It was, 



Fiu. 51. — Dried pupal wing of Samia cecropia. Region of the later eyespot 

 with crescent of white scales, which are finished and erect. (From Goldschmidt, 

 1920, Arch. Entwicklgmech. 47.) 



however, not observed in Kuehn's work on the flour moth, the 

 reason probably being that the very quick development of this 

 form makes it difficult to find the short stage when the phenome- 

 non may be made visible. 2 



In the flour moth, moreover, Kuehn's students Koehler (1932- 

 1935) and Braun (1936) found another nearly related fact. At 

 an early stage of development of the wing, the place of the future 

 zigzag bands is indicated by a zone of more numerous mitoses. 

 Two such waves of increased mitotic activity spread across the 

 wing: one in the hypodermal tissue; a second, in the scale- 

 forming cells. If a mutant (or a phenocopy) has a different 

 arrangement of the bands (shifting toward the base or the tip), 

 the pattern of mitoses, indicating the later dark areas, is corre- 

 spondingly shifted (Fig. 52). In addition, it was found that the 



1 Mostly unpublished work by Goldschmidt and Sueffert. 



2 It has been found meanwhile by W. Braun in the author's laboratory. 



