A Case of Hereditary Ataxia (?) in Pigeons. 57 



practically completely lost in the adult bird. The affected female 

 was bred to two different males. The derangement has been 

 inherited through four generations descended from either male. 



The affected offspring have shown many degrees of the lack 

 of muscular control (birds demonstrated). Some have shown 

 marked disturbances when young and have later recovered. 

 Others have at first been classed as normal and have later de- 

 veloped marked irregularity of movement. The more usual 

 manifestations of the disorder are: Nodding of the head, or nod- 

 ding and swaying of the head and neck; unsteady gait; tipping 

 (somersaulting) backwards or forwards; falling on the side; very 

 irregular flight, the bird even flying backwards. The same bird 

 often exhibits two, three or perhaps all of these irregularities. 

 Practically all affected birds are unable and uninclined to sit on 

 a perch, remaining constantly on the ground, or on a flat ledge. 

 In the most affected individuals there seem to be no movements 

 whatever of wholly normal coordination; in average cases, how- 

 ever, the disturbances are much increased under excitement, fear, 

 or any attempt at increased or more vigorous movement. In a few 

 cases the movements have seemed fairly normal when the bird 

 was at perfect rest. Several of the affected birds have mated 

 and produced young. Offspring from two affected birds have 

 not yet been obtained. 



About 175 young have been reared to the age at which the 

 disorder might be exhibited. Of this number 119 were classed 

 as normal and 46 as affected. The first mating of the original 

 female gave 33 normal and 3 affected. The affected offspring 

 when mated to their unaffected relatives gave 1 1 normals to 14 

 affected. Similar affected individuals outcrossed have yielded 

 4 normals to o affected. There is some evidence that more of 

 the affected individuals than normals die before attaining the 

 age required for classification. The details bearing on the method 

 of inheritance (chart demonstrated) make it appear that the new 

 character is, with some irregularities, a Mendelian recessive. 



The data are not sufficiently complete to permit a final state- 

 ment concerning the inheritance of the character as limited by sex. 

 That it is not wholly thus limited seems clear; possibly the sons 

 of unaffected mothers exhibit the disorder more often than do 



