224 BIOLOGY: GENERAL AND MEDICAL 



What is in the egg? What is the nature of these 

 maternal and paternal influences? How can they deter- 

 mine phylogeny and ontogeny? How can they deter- 

 mine every detail of the new being from its general 

 configuration to the finest details of internal structure; 

 from the color patterns upon its smallest feathers to the 

 choice of its food, the quality of its voice, or its future 

 habits of roosting in trees or building its nest on the 

 ground? 



Yet all this and more is accomplished without any 

 outside influence except the degree of warmth required 

 for the incubation. All of the forces that effect these 

 results are intrinsic in the egg, yet without any visible 

 explanation. Indeed some of the influences resident in 

 eggs do not appear to become active for years after 

 the adult individual has formed. Thus among human 

 beings we find it to be predetermined in the egg that 

 one shall lose his hair early or late, have his hair 

 whiten early or late, tend to corpulence at a certain age, 

 and even tend to die of apoplexy when a certain age is 

 reached. It seems, therefore, as though eggs are charged 

 with impulses so numerous, so diversified, and so persist- 

 ent as to determine the entire future of the individual 

 and leave nothing to chance or to circumstance. 



It is small wonder that matters of such surpassing 

 interest should have proved a fascinating study to 

 thinking men in all departments of learning and that 

 many theories should have been devised for their 

 explanation. 



Herbert Spencer 1 conceived that the form of each 

 living creature was determined by a " peculiarity in the 

 constitution of its physiological units, that these have 

 a special structure in which they tend to arrange them- 

 selves, just as have the simpler units of inorganic 

 matter." . . . 



" We must conclude that the likeness of any organism to either 

 parent is conveyed by the special tendencies of its physiological 



2 "Principles of Biology," I, p. 254, 1866. 



