PEENTISS: POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 259 



vestigial digit). Whether this underlying cause is reversion, will he 

 discussed Liter. 



cun. 



Fig. I). — Left pes of dog, showing hallux 

 fully developed. I, hallux; asg., astragalus; cac, 

 calcaneum; cub., cuhoid; ec'c!*?*., ecto-cuneiform; 

 en' cun., ento-cuneiform; ms'cun., meso-cunei- 

 fonn; tiav., navicular. 



en 



VIS 



cun. 



II. 



Fig. E. — Left pes of dog, showing 

 duplicated hallux, i, rudimentary meta- 

 tarsal of hallux; i«, i*, accessory digits; 

 asg., astragalus; cac, calcaneum; cub., 

 cuboid; ec't'wn., ecto-cuneiform; en' cun., 

 ento-cuneiform; ms'cun., nieso-cunei- 

 form; nav., navicular. 



IV. Polydactylism in the Fowl. 



Although the domestic hen is tetradactyle, the fifth digit was lost so 

 early in phylogeny that it never appears in polydactyle ahnormalities. 

 As the hallux of the pes is reduced, however, polydactylism is entirely 

 limited to this digit ; the condition is thus directly comparahle to that 



VOL. XL. — NO. 6 2 



