POLYDACTYLISM. 



19 



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



and an extra-toed parent. 



A. HOUDAN CROSSES, 



Pen 

 No. 



504 



525 



727 

 504 



Mother, 



No, 



8 or 11 



8 



11 



8 or 11 



"Y" 



121 



10-12 



Kace involved. 



Houdan 



....Do 



, ,,.Do 



....Do 



Dk. Brahma. . 



. ,..Do 



Wh, Leghorn . 



No, of 

 toes. 



5-5 

 5-5 

 5-5 

 5-5 

 4-4 

 4-4 

 4-4 



Father, 



No. 



13 



27 



S3] 



9 



Eaoe involved. 



Wh. Leghorn . 



Minorca 



Houdan 



....Do 



No, of 



toes. 



4r-4 



4-4 

 5-5 

 6-5 



Total (110),. 

 Percentages . 



Offspring. 



Types of toes. 



4-4 4-5 5-5 



30 

 27.3 



21 

 19,1 



8 

 8 

 7 



13 

 5 



18 

 



69 

 53,6 



Average. 



9,9 

 9,6 

 9,5 

 9.2 

 9.2 

 9.1 

 8,4 



9.26 



B, SILKIE CROSSES, 



Mother, 



Pen 



No, 



No. 



851 

 851 

 815 

 851 

 734 

 851 

 851 

 851 

 734 

 734 

 851 

 851 

 744 

 744 

 851 



1002 



3410 



131 



2073 



841 



838 



2299 



5567 



840 



1002 



840 



841 



777 



496 



Kace. 



Cochin 



...Do 



,,,Do 



.,.Do 



,..Do 



,..Do 



...Do 



...Do 



...Do 



...Do 



...Do 



...Do 



Silkie 



....Do 



Cochin 



No. 



of 



toes. 



4_4 

 4-4 

 4-4 



4r-4 



4-4 

 4-4 



4r-4 



4-4 



4-4 

 4-4 

 *6-6 

 6-6 

 4-4 



Father. 



No. 



7526 

 7526 



774 

 7526 



774 

 7526 

 7526 

 7526 

 7526 



774 

 7526 

 7526 

 1176 

 1176 

 7526 



Race. 



SiMe 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



..Do 



Wh. Leghorn. . . 



...Do 



Silkie 



No 



of 



toes. 



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 

 6-6 



Total (138). 



Offspring. 



Types of toe8,t 



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



93 



12 



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 

 9,60 



10,13 



* Of the reduced triplex type (f). t s, 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 polydactylism 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 Houdans (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 Fj generation of Silkies never have as 



