ii 4 RETROGRESSION 



when opposed to an enemy, she would erect her hackles and show 

 fight. Thus every character, even to the instinct and manner of 

 fighting, must have lain dormant in this hen as long as her ovaria 

 continued to act. The females of two kinds of deer, when old, 

 have been known to acquire horns ; and as Hunter has remarked, 

 we see something of an analogous nature in the human species." * 

 C. E. Walker injected an emulsion of testes into hens, thus supply- 

 ing the necessary stimuli, and caused them to develop the combs, 

 wattles, and warlike disposition of cocks. 2 Professor Giard, Geoffrey 

 Smith and others have shown that when the testes of crabs are 

 destroyed by parasites (Rhizocephala) the males may develop all 

 the characters of females, including ovaries. In some cases the 

 animal becomes a perfect hermaphrodite. 3 Mr J. H. Orton has de- 

 monstrated that the molluscs Crepidula fornicata and Calyptrcea 

 chinensis are males at first but become females later. 4 



187. In addition to the temporary latency typically seen in the 

 case of the sexual characters, there is a more permanent form. 

 "Besides visible changes which it [the germ-cell] undergoes, we 

 must believe that it is crowded with invisible characters proper to 

 both sexes, to both the right and the left sides of the body, and to 

 a long line of male and female ancestors separated by hundreds 

 and even thousands of generations from the present time ; and these 

 characters, like those written on paper in invisible ink, lie ready to 

 be evolved whenever the organism is disturbed by certain known 

 or unknown conditions." 5 Thus individuals derived from 

 domesticated breeds of pigeons or fowls may reproduce the 

 characters of extremely remote wild ancestors. In cross-breeding 

 between domesticated varieties the re-appearance of hitherto latent 

 ancestral characters is so common that Darwin declared " we must 

 conclude that a tendency to this peculiar form of transmission is 

 an integral part of the general law of inheritance." 6 



1 88. There is a good deal of evidence that latency is influenced 

 directly, in a measure at least, by the environment. Thus Ewart 

 rendered latent at will the male or female characters of rabbits. 

 Amongst bees the female characters develop fully only under 

 certain conditions of environment in which, apparently, nutriment 



1 Animals and Plants, vol. ii. p. 26. 



8 The Influence of the Testes upon the Secondary Sexual Characters of Fowls, 1908. 



3 Fauna und Flora des Golfes von Neapel, Monograph, 29 ; Rhizocephala, 

 Geoffrey Smith, Berlin, 1906. 



4 Proc. Roy. Soc., B., vol. Ixxxi. pp. 68-84. 

 6 Animals and Plants, vol. ii. pp. 35-6. 



6 Loc. cit. t vol. ii. p. 31. 



