J. E. DUERDEN 175 



incomplete break occurs over both joints, the scales being vestigial over 

 the first and fragmentary over the second. 



TABLE XVI. 



Breeders: 



North African cock, No. 84 No break, slight narrowing at the first joint 



North African hen. No. 116 Two incomplete breaks ; first vestigial scales, 



second fragmentary 

 Chicks : 



Three— Nos. 1, 3, 10 ... Two breaks, both well-defined 



One — No. 8 ... ... ... One break well-defined, scales over second joint, 



scarcely narrow 

 Three — Nos. 2, 4, 7 ... No break, but scales vej-y narrow at both joints 



Three — Nos 5, 6, 9... ... No break ; first joint scales very narrow, second 



scarcely narrow 



Four successive stages are here represented in the breaking-up of 

 the digital scutellation. Three chicks display two very decided breaks 

 without any intervening small scales; one shows a well-defined single 

 break only ; three have no break, but the scales over the first joint are very 

 narrow and are beginning to fragment over the second ; while three 

 have the scales at the first joint very narrow, but scarcely any change 

 over the second. In each chick there is an accentuation, on definitely 

 prescribed lines, of the breaking-up compared with that in the parent 

 cock, while the three with two breaks represent an advance on the stage 

 reached in the parent hen. If we admit that the incoming of some 

 inhibitory or break influence is in progress, the accentuations can be 

 readily understood, as well as the departures from the expected Mendelian 

 proportions. 



An accentuation in the loss of scales is still more marked in a case 

 of in-breeding. The series is as follows : 



TABLE XVIL 



Grand-Parents : 



North African cock. No. 9 No break 



South African hen, No. 225 Break 



F^ Chicks : 



Three— Nos. 180, 181, 182 No break, but narrowing 



One — No. 179 Break complete on one toe, incomplete on other 



Parents : 



Cross-bred cock. No. 182 ... No break, but narrowing 



Cross-bred hen, No. 179 ... Break complete on one toe, incomplete on other 



F2 Chicks : 



One — No. 4... ... ... No break, but narrowing 



One — No. 2... ... ... Single break 



Two — Nos. 1, 3 Two breaks, well-defined 



A series of chicks later than the above has been obtained, but they 

 are not so reliable for purely genetic purposes seeing that the cross-bred 



