No. 613] INHERITANCE IN F ANT AIL PIGEON 



17 



ords were kept of the entire color of each bird, it is not 

 now possible to find out how closely the complete pattern 

 would correspond with the tail color. In general, how- 

 ever, in these birds the tail is a partial index, at least— a 

 fair sample, perhaps— of the entire color. 



of Tail Feathers 



Darwin suggests a " correlation" between the absence 

 of the oil gland and the increased number of tail feathers. 

 Such a relation might be a direct correlation in the sense 

 that the overdevelopment of the tail feathers suppresses 

 or tends to suppress the development of the oil gland that 

 is situated on the uropygium just above the base of the 

 tail feathers. If this were the true interpretation of the 

 condition in the fantail, one would expect to find in F 1 

 and F 2 all degrees of development of the oil gland. If, 

 on the other hand, the absence of the oil gland is an in- 

 herited peculiarity having nothing directly to do with the 

 number of feathers, then in the F 2 series we might expect 

 to find a numerical relation indicating its mode of inherit- 

 ance. Unfortunately the pedigrees of the normal tailed 

 pigeons that had been mated to the fantail s were un- 

 known. While the oil glands may be occasionally absent, 

 in domesticated pigeons, it is highly improbable that any 

 of the homers used in the experiment carried such a fac- 

 tor. In classifying the ¥ 1 and F 2 birds according to the 

 condition of the oil gland three classes were recognized. 

 First, " double" glands, those with the right and left sides 

 almost separate, each with a separate opening; second, 

 "single" glands, those with the halves united more closely 

 and with but one external outlet ; 7 third, those with no oil 

 glands. The results are given in graphs of Figs. 10-11. 



The few F t birds available when the oil gland was 

 studied show a wide range of variability ; all but one were 

 double, Fig. 10 (above). This doubling might be due to 



