DEGENERA TION. 2 1 



kingdom. There is very strong reason to believe 

 that it is a general law of transmission or inheritance, 

 that structural characteristics appear in the growth 

 of a young organism in the order in which those 

 characteristics have been acquired by its ancestors. 

 At first the ^g^ of a dog represents (imperfectly, it is 

 true,) in form and structure the earliest ancestors of the 

 dog ; a few days later it has the form and structure 

 of somewhat later ancestors; later still the embryo 



Fig. I. — An egg: a single corpuscle of protoplasm with nucleus h c, and body a. 



dog resembles less remote ancestors ; until at last 

 it reaches the degree of elaboration proper to its 

 immediate forefathers. 



Accordingly the phases of development or growth 

 of the young are a brief recapitulation of the phases of 

 form through which the ancestors of the young crea- 

 ture have passed. In some animals this recapitulation 

 is more, in others it is less complete. Sometimes the 

 changes are hurried through and disguised, but we find 



