26 CALIFORNIA ACADP^MY OF SCIENCES. 



independently of Romanes.* When any part or the 

 whole of an individual is retarded in its growth, so that 

 the animal begins to breed before reaching maturity, 

 Cope holds that the descendents will be deficient in such 

 parts as were not fully developed in the parent. The 

 statement of the action of this law in producing degene- 

 ration of parts is as follows: " 'Retardation' continued 

 terminates in extinction. Examples of this result are 

 common ; among the best known are those of the atrophy 

 of the organs of sight in animals inhabiting caves. * '"'' 

 I would suggest that the process of reduction illustrates 

 the law of ' retardation ' accompanied by another phe- 

 nomenon. Where characters which appear latest in em- 

 bryonic history are lost, we have simple retardation — 

 that is, the animal in successive generations fails to 

 grow up to the highest point of completion, falling 

 farther and farther back, thus presenting an increasingly 

 slower growth in the special direction in question. 

 Where, as in the presence of eyes, we have a character 

 early assumed in embryonic life, retardation] presents a 

 somewhat different phase. Each successive generation, 

 it is true, fails to come up to the completeness of its pre- 

 decessor at maturity, and thus exhibits 'retardation;' 

 but this process of reduction of rate of growth is followed 

 by its termination in the part long before growth has 

 ceased in other organs. This is an exaggeration of 

 retardation, and means the early termination of the 

 process of force-conversion, which has been previously 

 diminishing steadily in activity." 



The subject of use and disuse need not be considered 

 in further detail. From the above it is evident that there 

 are many explanations of the phenomena of degenera- 

 tion and that pammixis cannot be at best more than one 

 of several factors. 



" Origin of the Fittest, p. 13. 



