IQIS] 



BARTLETT—MASS MUTA TION 



435 



they may be called for convenience, exhibit mass mutability super- 

 posed upon their ordinary behavior in heredity. In order to present 

 the data in regard to this point it will be necessary to anticipate 

 somewhat the publication of the next article of this series. 



Among the mutations of 0. pratincola which have been obtained 

 both from Lexington E and from the strains showing only ordinary 



Fig. 3. — Progeny of Lexington E-5, pan 7 (part of culture 3; the remainder is 

 sllo^\^l in fig, 2; see table II); the pan contains 26 plants, which were classified at 

 maturity as follows: 



