POLYDACTYLISM. 



Table 18. 



26 



No direct relation here appears between development of the extra toe 

 in the parents and the average number of toes in the offspring. 



Of the Silkies, 3 hens were used in 5 matings. The same 6-toed cock 

 (No. 774) was employed throughout (table 19). 



Table 19. 



In table 19 the series a of observed average numbers of fiUal toes 

 (10.3, 10.9, 10.0) and the series b obtained by assigning the typical full 

 number to all reduced t3T)es (11.4, 11.4, 10.5) are decidedly irregular. 

 There is, however, between the parental and the fihal series a correlation 

 of +0.250 ±0.070. This indicates a shght tendency for the number of toes 

 in the progeny to vary with those of the parentage. 



The second set of data is derived from special matings made with 

 hybrids between Houdans and 4-toed races. On the one hand, in pens 728 

 and 813, cocks with well-developed toes of the duplex type were mated 

 with hens as nearly as possible of the same sort; while in pens 765, 769, 

 and 820 cocks with small, imperfectly separated toes (probably of the duplex 

 type *) were mated with hens as far as possible of the same sort. 



Tables 20, 21, and 22 give in detail and in summary the distribution 

 of types of polydactyhsm in the famihes from well-developed and in those 

 from poorly developed parents. They show a great difference between the 

 offspring of parents with good extra-toe (table 20) and those with poor 

 extra-toe (table 21). The former yield over 80 per cent offspring with 5 toes 

 or more on one or both feet, while the latter yield about 57 per cent of such. 



* I say probably of the duplex type because the cock of pen 769 had a distally split toe on the right foot, reminding 

 somewhat of the redtuxd triplex type. But as the left foot had a typical duplex thumb, and the triplex is not common in 

 Houdans, it should probably be classed as duplex. 



