The types of syndactylism which have appeared in my flock form a rather extensive series. First, (_A_) the single web, which, in my specimens, always occupies the interspace between digits III and IV. This is the same interval which is most apt to show the web in syndactylism of the human hand, and, it is suggestive to note, it is this interval that is filled in those wading birds that have the single web only between the toes (_e.g._, _Cursorius_, _Glareola_, _Vanellus_, _Squatarola_, _Charadrius_, _Limosa_, _Machetes_, _Himantopus_); second, there is (_B_) the double web, one-seventh as common, which always occupies the interspaces between the digits II-III and III-IV. On another basis, the syndactyl feet may be classified as: (_a_) toes adherent, web small in extent, and (_b_) toes distant, web broad. I have found the narrow web only between digits III and IV. It is one-eighth as common as the broad-webbed type. The broad, double web approaches closely to the type found normally in swans, geese, and ducks. Finally, the syndactyl feet may be classified as: α, straight-toed, or β, curve-toed. Class α is to class β in frequency as 2:1. In the typical curve-toed syndactyl foot the web between III and IV is complete to the nails of each; in fact, in extreme cases the nails of the two toes are more or less fused together. From the fused nails the middle toe, being the longer, passes in a curve to the distal end of the metatarsus. The D-shaped interspace between the curved III and straight IV toe is filled with the web. In other cases the nails are merely approximated and the middle toe is slightly curved. In three instances (4 per cent of all) the outer toe (IV) is curved toward the (straight) median toe (class β´). As stated, the polydactyl offspring trace back their ancestry to No. 121; her feet both show the double, broad, straight-toed type (_Bb_α). We shall attempt in the following paragraphs to trace the heredity of her type of polydactylism and of the others that have subsequently arisen. B. RESULTS OF HYBRIDIZATION. In taking up the results of breeding experiments to test the method of inheritance of syndactylism, it will be best first to give in a table all pens in which the character showed itself, with the frequency of the different types of foot in them (table 23).