STUDIES IX THE EXPERIMENTAL ANALYSIS OF SEX. 597 



sidering" the wide limits of variation iu uninjectedbirdSj from 

 to 78 per cent., it is certain tliat no significance can be 

 attached to this single case. Neither did the behaviour of 

 this bird, subsequent to the cessation of the injections^ lend 

 any support to the idea that the injections were the cause of 

 the increase. In Dr. Walker's two birds, after the injections 

 ceased, the combs steadily shrank back nearly to their 

 original dimensions. In my bird the comb shrank a little, 

 but then afterwards increased again. Doubtless a larger 

 series of measurements during the spring months on white 

 Leghorn fowls would reveal as wide a range of fluctuation iu 

 untreated as in this injected bird. I have now under 

 observation four Leghorn hens, whose combs have decreased 

 to less than half their area during moulting, and doubtless 

 they will again increase iu the spring.^ The measurements 

 both on injected and control birds establish the fact that in 

 adult as well as in young hens the comb is in a state of 

 fluctuating growth, the fluctuations being often marked 

 within a few days. If we attempt to correlate the variations 

 in the comb with the vaiiations of both'-weight as given in 

 the fourth column of the schedule, it will be seen that a 

 simultaneous increase in the comb and in the body-weight is 

 only to be observed in the young hens in Experiment 3, 

 where such a correspondence would be naturally expected. 

 It appears to me that an increase of comb is to be observed 

 just before the hens begin laying.- Thus a reference to the 

 fifth column in the schedule will show that the correspond- 

 ence is marked, especially in BirdXo. 7. It will be seen that 

 the increase of comb is not confined to any particular period 

 of the year, but may take place in autumn as well as in 

 spring. 



' This supposition has been oonfirmed, a normal Leghorn hen giving 

 a percentage increase of 130 in twenty days. This is the greatest 

 increase observed in any bird, normal or injected. 



- In the next study evidence will be prodnced proving that the 

 sndden increase of the comb is strictly correlated with egg-laying. 



