620 



THE WONDEF OF LIFE 



at least, it seems highly probable that these richly inner- 

 vated, though much reduced structures, play some role 

 in connexion with food- getting. 

 Living Fossils. Of great in- 

 terest in this connexion are those 

 old-world types such as Peripatus 

 and Limulus, Polypterus and the 

 Dipnoi, Sphenodon and the Mono - 

 tremes survivors of ancient races. 

 One of these living fossils is 

 the hoatzin (Opisthocomus), an 

 extremely ancient and isolated 

 type, frequenting the lower 

 Amazon and surrounding terri- 

 tory. One of its primitive 

 features is the quadrupedal 

 character of the young, which 

 use their fore-limbs for creeping 

 about with on the branches. 

 They also dive and swim well. 

 There are external claws on the 

 first and second fingers and a 

 vestigial claw on the third. The 

 hand-like use of the wing is 

 present in the adults as well, who 

 never fly if they can help it. Mr. 

 Beebe notes that ' their method 

 of arboreal locomotion is to push 

 and flop from branch to branch '. 

 Their weakness of flight is doubt- 

 less in part due to a curious 

 specialization, that the crop has 



FIG. 97. Peripatus, an 

 ancient type, in some re- 

 spects linking segmented 

 worms to Insects. The 

 figure shows antennae, 

 simple eyes, simple 

 clawed appendages, and 

 an unsegmented some- 

 what cater pillar-like 

 body. (After Balfour.) 



