PHYLOGENY. 133 



Looking at the skeleton, we observe the following 

 successional modifications : 



First, as to the feet, and (A) the digits. The Con- 

 dylarthra have five digits on both feet, and they are 

 plantigrade. This character is retained in their de- 

 scendants of the lines of Anthropomorpha, Quadru- 

 mana, and Hyracoidea, also in the Bunotheria, Eden- 

 tata, and most of the Glires. In some of the Amblypoda 

 and in the Proboscidia the palm and heel are a little 

 raised. In the Carnivora and Diplarthra the heel is 

 raised, often very high, above the ground, and the 

 number of toes is diminished, as is well known, to two 

 in the Artiodactyla and one in the Perissodactyla. 

 (B) The tarsus and carpus. In the Condylarthra and 

 most of the Creodonta the bones of the two series in 

 the carpus and tarsus are opposite each other, so as to 

 form continuous and separate longitudinal series of 

 bones. This continues to be the case in the Hyracoi- 

 dea and many of the Quadrumana, but in the anthro- 

 poid apes and man the second row is displaced inwards 

 so as to alternate with the first row, thus interrupting 

 the series in the longitudinal direction, and forming a 

 stronger structure than that of the Condylarthra. In 

 the bunotherian, rodent, and edentate series, the tar- 

 sus continues to be without alternation, as in the Con- 

 dylarthra, and is generally identical in the Carnivora. 

 In the hoofed series proper it undergoes change. In 

 the Proboscidia the carpus continues linear, while the 

 tarsus alternates. In the Amblypoda the tarsus alter- 

 nates in another fashion, and the carpal bones are on 

 the inner side linear, and on the outer side alternating. 

 The complete interlocking by universal alternation of 

 the two carpal series is only found in the Diplarthra. 

 1 (C) As to the ankle-joint. In most of the Condylarthra 



