THE RECAPITULATION THEORY 333 



form that is ideally inferior is very ^possible. To 

 animals living in profound darkness_the__possession 

 of eyes is of no advantage, and forms devoid of 

 eyes would not merely lose nothing_^thereby, but 



would actually gain, inasmuch as they would 



escape the dangers that might arise from injury 

 to a delicate and complicated organ. In extreme 

 cases, as in animals leading a parasitic existence, 

 the conditions of life may be juch as to render 

 locomotor, digestive, sensory, and other organs 

 entirely useless ; and in such cases those forms 

 will be best in harmony with their surroundings 

 which avoid the waste of_energy resulting from the 

 formation and maintenance of theae organs. 



Animals which have in this wav^fallen from the 

 high estate of their forefathers, which have lost 

 organs or systems which their progenitors possessed, 

 are commonly called degenerate. The"principlej3f 

 degeneration, recognised by Darwin as a possible, 

 and under certain conditions a necessary conse- 

 quence of his theory of natural selectioji^has been 

 since advocated strongly by Dohrn, and later by 

 Lankfler~ia-ari EveningJDiscourse delivered before 

 the Association at the Sheffield Meeting in 1879. 

 Both Dohrn and Lankester suggested that degenera- 

 tion occurred mucITntore "WldelyjKan was generally 

 recognised f 



In animals which are parasitic when adult, but 

 free swimming in their early stages, as in the case 

 of the Rhizocephala whose life-history was so 

 admirably worked out by Fritz Mtiller, degenera- 

 tion is clear enough. So also is it in the case of 



