Il6 PROC. COTTESWOLD CLUB vol. xm. (2) 



VIII. Appendix : 



UNDUE ACCELERATION, AND RETARDATION, OF 

 DEVELOPMENT 



Acceleration of development, or the inheritance of 

 characters at an earlier stage in each generation expresses 

 the process whereby the ontogenetic history recapitulates 

 the successive stages of phylogeny. But though the re- 

 capitulation may be fairly accurate when each character is 

 considered independently, yet it appears to be inexact 

 when the whole series of characters of a particular stage is 

 reviewed. Thus while in regard to many characters the 

 normal acceleration of development has taken place, yet 

 in others undue acceleration has become necessary to fit 

 the organism for the part it has to perform in life, and 

 in others again retardation has taken place. 



The most noted case of retardation of development is 

 that of the wisdom teeth of Man. They appear late in 

 life, as if they were a character only recently developed ; 

 but actually they were very well developed in the pre- 

 human ancestors. 



The post-natal development of teeth in Man is a case of 

 retardation. 



The inability to see in the case of many animals until 

 some time after birth is again retardation. 



The inability to walk in the case of many young animals 

 is an instance of retardation. 



Some of the figures given in Plates I. and II. illustrate 

 what may be termed the unequal rate of development in 

 regard to certain characters. Thus in fig. i is the quad- 

 rupedal gait which would have characterised the old early 

 Catarrhine ancestor. But he would have had a hairy 

 body ; here the body is destitute of hair, and that was a 

 character of primitive Man. Again, the hind foot shows 

 acceleration of the human foot-character : the quadrupedal 



