POLYDACTYLISM. 



19 



Table 10. Frequency of the various types of toes in the first hybrid generation between a normal 



and an extra-toed parent. 



A. HOUDAN CROSSES. 



Pen 

 No. 



Mother. 



No. 



Race involved. 



504 



525 

 727 

 504 



8 or 11 



8 



11 



8 or 11 



"Y" 



121 



10-12 



Houdan 5-5 



...Do 



....Do 



....Do 



Dk. Brahma. 

 ....Do 



No. of 

 toea. 



5-5 

 5-5 

 5-5 

 4-4 

 4-4 

 Wh. Leghorn 44 



Father. 



No. 



13 

 27 



[ssi 



9 



Offspring. 



Race involved. 



No. of Types of toes. 



Wh. Leghorn . 



Minorca 



Houdan 



....Do 



4-4 



4-4 

 5-5 

 5-5 



Total (110).. 

 Percentages. 



44 45 55 



^ Average, 



30 

 27.3 



21 

 19.1 



8 

 8 

 7 



13 

 5 



18 

 



9.9 

 9.6 

 9.5 

 9.2 

 9.2 

 9.1 

 8.4 



59 

 53.6 



9.26 



B. SILKIE CROSSES. 



Mother. 



Pen 



No. 



No. 



Race. 



851 



851 



815 



851 



734 



851 



851 



851 



734 



734 j 



851 I 



851 



744 



744 



851 , 



1002 



3410 

 131 



2073 

 841 

 838 



2299 



5567 

 840 



1002 

 840 

 841 

 777 

 496 



6956 



i No. 

 I of 

 toes. 



Cochin 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



Do 



Do 



..Do 



..Do I 4-4 



Silkie 1*5-6 



Do 6-6 



Cochin 4-4 



4-4 

 4-4 



4r-i 



4-4 

 4-4 

 4-4 

 4-4 

 4-4 

 4-4 

 4-4 

 4-4 



Father. 



No. 



Race. 



7526 

 7526 



774 

 7526 



774 

 7526 

 7526 

 7526 

 7626 



774 

 7526 

 7526 

 1176 

 1176 



I No 

 ! of 

 toes. 



Silkie 



....Do 



...Do 



...Do 



...Do 



. ...Do 



...Do 



...Do 



...Do 



...Do 



...Do 



...Do 



Wh. Leghorn.. . 



Do. 



6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 6-6 

 4-4 

 4-4 



7526 Silkie 6-6 



Offspring. 



Types of toes.f 



sd'. sd. d'd'. d'd. dd. st'. d't'. dt'. ft'. 



1? 



Total (138) 6 



Average. 



10.78 

 10.43 

 10.33 

 10.33 

 10.25 

 10.25 

 10.14 

 10.08 

 10.00 

 10.00 

 10.00 

 10.00 

 10.00 

 9.93 

 9.50 



12 



10.13 



Of the reduced triplex type (f). t Si means type of single thumb; d, duplex type; d', reduced duplex; t', reduced triplex. 



Houdan crosses. For 27 per cent of the latter are non-polydactyl, while, 

 taking the table as it stands, at most only about 4 per cent and (as just 

 stated) probably none of the Silkie offspring were of the typical single- 

 thumbed type. Also the average degree of polydactyhsm is much greater 

 in the Silkie than in the Houdan crosses. This excess is in part due to the 

 different method of counting toes in the Silkie and the Houdan hybrids; 

 for whereas in the latter the visible toes are counted as equivalent units, 

 in the former in the case of each reduced type one unit more is assigned 

 than appears. The actual number of toes occurring in the Silkie hybrids 

 was also calculated, and it was found that this still averaged higher than 

 that of the Hcudans (9.45 as opposed to 9.26). 



In hybrids of both classes the greatest number of toes occurring on one 

 foot never exceeds the greatest number possessed by its parents; indeed, 

 the most polydactyl hybrids of the F, generation of Silkies never have as 



