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THE AMERICAN NATURALIST [Vol. L 



cedures female is mated with female, and male with male. 

 Such pairs— from a very few selected pairs of parents- 

 are kept mated for a period of six months. The three 

 and one half years that this study has been pursued has 

 enabled us— using 30 to 50 birds— to test one and the 

 same bird with seven others. Most of the birds used— 

 for lack of success with the incessantly fighting males — 

 have been females, and most of the seven successive tests 

 with each bird have been made with its sisters of the same 

 series. The members of the pairs are kept apart except 

 when under observation; when put together— as they are 

 twice daily— the records are taken of those females of 

 the pair which behave as males in copulation with their 

 mates. Three facts are definitely established by the data 

 obtained: (1) The females of the orientalis X alba cross 

 (they are dark in color) are more male-like in their sex 

 behavior than the females of the reciprocal cross (these 

 are white in color). (2) Females hatched from eggs laid 

 earlier in the season are more masculine in their sex be- 

 havior than are their own full sisters hatched later in 

 the season. And, several grades of females can be thus 

 seriated according to season of hatching. (3) The female 

 hatched from the first egg of the clutch is more masculine 

 than her sister hatched from the second of the clutch 

 in a great majority of the cases. And in nearly all these 

 latter matings the more masculine bird is so decidedly so 

 that she takes the part of the male a full 100 per cent, of 

 the time in copulating with her very feminine clutch-mate 

 sister. 



A fuller account of this situation was given, with the 

 assistance of charts too large to exhibit or describe here, 

 before the Society of Zoologists in 1913. 13 The nature 

 of this behavior has been adequately recorded by means 

 of moving-picture films. Such records were also made 

 showing the reversal of the known sex-behavior of such 

 pairs by means of appropriate injections of ovarian and 

 testicular extracts. Those films were demonstrated in 

 this hall— or in one near-by— in connection with an ad- 



i3 Abstract in Science, March 20, 1914. - 



