DEPARTMENT OF EXPERIMENTAL EVOLUTION. 119 



in behavior than are their own sisters hatched late in the season. Dr. 

 Riddle has succeeded in some cases in reversing the sex-behavior. 

 Thus, if extracts from the ovary of a pigeon be injected into those 

 females that are behaving like males they come to behave like females. 

 Contrariwise, if testicular extract be injected into those females that 

 are acting like females they come to act like males. The full signifi- 

 cance of this result is still obscure. The sex-behavior of a bird is 

 probably determined by internal secretions from its sex-glands carried 

 to its central nervous system. On this hypothesis the quality of the 

 internal secretions of the ovaries of birds that act like males must be 

 different from those of birds that act like females. The effect of the 

 injected extract may perhaps be regarded as superior to that induced 

 by the natural secretion of the ovaries. 



Sex-linked Inheritance in Lychnis, G. H. Shull. 



The series of studies on Lychnis, which exhibits certain character- 

 istics that render it critical for the study, has been continued by the use 

 of a narrow-leafed mutant that depends upon a sex-limited defect. 

 The original narrow-leafed plant was a male which when crossed with 

 broad-leafed females produced broad-leafed males and broad-leafed 

 females; but when these were bred together they produced (in F2) 

 broad-leafed and narrow-leafed progeny. The narrow-leafed progeny 

 were all males, but the broad-leafed progeny were partly males, partly 

 females. Thus the narrow-leafed condition shows itself in F2 only in 

 males, though half of the females carry the determiner of narrowness 

 in half of their eggs, as experiment proved. All of these broad-leafed 

 F2 females were crossed with the narrow-leafed males, and it was 

 expected that in F3 many narrow-leafed females would appear from 

 the union of sperms carrying both the female character and the deter- 

 miner for narrowness with eggs of the same constitution. It was an 

 unexpected and baffling result that practically no narrow-leafed females 

 occurred. This unexpected failure to produce narrow-leafed females 

 in the F3 was experimentally shown to be due to the absence or ineffi- 

 ciency in the narrow-leafed males of sperms carrying the determiner for 

 femaleness, for crosses between these same narrow-leafed males and 

 homozygous broad-leafed females resulted likewise in only a rare pro- 

 duction of females. There is a theoretical reason for believing that the 

 mutation first occurred in a male-bearing sperm and that a large section 

 of the species (if not all of it) is characterized by sperms defective in 

 regard to the broad-leaf determiner. Such defect could appear somati- 

 cally only after an egg had also lost its determiner for broad-leaf, as the 

 narrow-leaf is a recessive character. In support of this conclusion, a 

 broad-leafed male and a broad-leafed hermaphrodite, both from points 

 in the United States far from the home of the original mutant, were 

 tested and were found to be heterozygous for the defect; that is, they 



