THE GENEALOGY OF ANIMALS 85 



and six, while ten is divisible by two and five 

 only. 



How helpless human beings are — in fact, how 

 helpless all beings are ! How hopelessly dependent 

 we are upon the past, and how impossible it is to 

 be really original ! What the future will be depends 

 upon what the present is, for the future will grow 

 out of, and inherit, the present. What the present 

 is depends upon what the past was, for the present 

 has grown out of, and inherited, the past. And 

 what the past was depends upon a remoter past 

 from which it evolved, and so on. There is no 

 end anywhere of dependence, either forward or 

 backward. Every fact, from an idea to a sun, is 

 a contingent link in an eternal chain* 



From the amphibians (probably from extinct 

 forms, not from living) there arose the highest 

 three classes of vertebrates — the true reptiles, the 

 birds, and the mammals — all of whom have lungs 

 and breathe air from the beginning to the end of 

 their days. Gills, as organs of breathing, disappear 

 forever, being changed, as has been said, into 

 parts of the organs of mastication and hearing. In 

 the reptiles first appear those organs which in the 

 highest races overflow on occasions of tenderness 

 and grief, the tear glands. These organs are, 

 however, in our cold-blooded antecedents, organs 

 of ocular lubrication rather than of weeping. 

 There are but four small orders of existing reptiles 

 — snakes, turtles, lizards, and crocodilians. These 

 are the pygmean descendants of a mighty line, the 

 last of a dynasty which during the greater part of 



