SECT. XXXIX. 4. GENERATION. 5^ 



diftention of a primordial neft of germs, included 

 one within another, like the cups of a conjurer. 



Fourthly, when we revolve in our minds the 

 great fimilarity of ftrudure, which obtains in all 

 the warm-blooded animals, as well quadrupeds, 

 birds, and amphibious animals, as in mankind ; 

 from the moufe and bat to the elephant and whale ; 

 one is led to conclude, that they have alike been 

 produced from a fimilar living filament. In fome 

 this filament in its advance to maturity has acquired 

 hands and fingers, with a fine fenfe of touch, as in 

 mankind. In others it has acquired claws or talons, 

 as in tigers and eagles. In others, toes with an 

 intervening web or membrane, as in feals and geefe* 

 In others it has acquired cloven hoofs, as in cows 

 and fwine ; and whole hoofs in others, as in the 

 horfe. While in the bird kind, this original living 

 filament has put forth wings inftead of arms or legs, 

 and feathers inftead of hair. In fome it has pro- 

 truded horns on the forehead inftead of teeth in the 

 forepart of the upper jaw ; in others tufhes inftead 

 of horns ; and in others beaks inftead of either. 

 And all this exactly as is daily fcen in the tranf- 

 mutations of the tadpole, which acquires legs and 

 lungs, when he wants them ; and lofes his tail, 

 when it is no longer of fervice to him. 



Fifthly, from their firft rudiment, or primordium, 

 to the termination of their lives, all animals under- 

 go perpetual transformations ; which are in part 

 produced by their own exertions in confequence of 

 their deiires and averfions, of their pleafures and 

 their pains, or of irritations, or of affociations; and 

 many of thefe acquired forms or propenfuies are 

 transmitted to their pofterity. See Sect, XXXI. j. 



As air and water are fupplied to animals in fuffi- 

 cient profufion, the three great objecls of defire, 

 which have changed the forms of many animals by 

 tfyeir exertions to gratify them, are thofe of luft, 



hunger^ 



