1 14 E VOL UTION AND DISEASE. 



The apparent rarity of supernumerary fore limbs, in 

 comparison with hind limbs, will be dealt with when 

 considering the question of dichotomy as manifested in 

 the trunk. 



In cats and dogs dichotomy of the terminal segments 

 of the fore and hind-limbs is fairly often seen, and a 

 five-legged dog is one of the usual exhibits at a penny 



FIG. 62. A Dove with an accessory wing, probably 

 due to dichotomy. 



monstrosity-show. An uncommon example is repre- 

 sented in fig. 63 ; it is a sheep with an extra fore-limb 

 attached to the scapula. The terminal segment is re- 

 duplicated. Dissection of the parts seemed to show that 

 the abnormal limb was due to dichotomy of the limb 

 axis, but this explanation is not altogether satisfactory. 

 From supernumerary limbs we may now pass to the 

 consideration of what are commonly known as- double 



