130 EVOLUTION AND DISEASE. 
lived to twenty, thirty, or more years. Of the more 
remarkable cases may be mentioned Jean B. dos Santos 
of Portugal, and Blanche Dumas. The mode of origin 
of paired pelvic limbs has been especially studied by 
Professor Cleland. This anatomist has clearly demon- 
strated that many of these are due to posterior 
Fic. 74.—A Drake with a pair of supernumerary legs. 
dichotomy leading to reduplication of the pelvis. He 
further points out that in living specimens of posterior 
dichotomy, the functional limbs belong to opposite 
pelves. In some it will be right limb of the right 
pelvis and the left limb of the left pelvis. In such a 
case the adjacent sides of the pelves and the associated 
