208 FROM THE GREEKS TO DARWIN 



changes in their own structure, these changes be- 

 ing transmitted to their offspring. 



In this chapter upon Generation {i, e., Hered- 

 ity), he throws out a wealth of suggestion and 

 inquiry which indicates a thorough appreciation 

 of the problems which were yet to be solved, as 

 well as of the broader aspects of Evolution. He 

 touches upon embryology, comparative anatomy, 

 the coloring of animals, artificial selection, and 

 treats environment almost in its broadest sense. 



We may briefly follow the outline of his argu- 

 ment for Evolution in the Zoonomia of the year 

 1794. He says, in effect, that when we revolve in 

 our minds the metamorphoses of animals, as 

 from the tadpole to the frog; secondly, the 

 changes produced by artificial cultivation, as in 

 the breeds of horses, dogs, and sheep ; thirdly, the 

 changes produced by conditions of climate and 

 of season, as in the sheep of warm climates being 

 covered with hair instead of wool, and the hares 

 and partridges of northern climates becoming 

 white in winter: when, further, we observe the 

 changes of structure produced by habit, as seen 

 especially in men of different occupations ; or the 

 changes produced by artificial mutilation and 

 prenatal influences, as in the crossing of species 

 and production of monsters ; fourth, when we ob- 

 serve the essential unity of plan in all warm- 

 blooded animals — we are led to conclude that 



