THE FACTORS WHICH DETERMINE SEX 653 



phenomenon are supplied by certain animals. Thus Potts * has 

 shown that in the male Hermit Crab ova make their appearance 

 in the testes, and the secondary sexual characters become modi- 

 fied in the direction of the female as a consequence of the animal 

 being affected by the parasite Peltogaster. Similar changes 

 occur in a number of other animals belonging to widely different 

 groups, but they are especially common in the Crustacea. 

 Smith, who has paid considerable attention to this subject, 2 

 explains the phenomenon by assuming that the males, in order to 

 cope with the drain on the system caused by the parasites, have 

 to increase their vegetative activity, and that they do this by 

 suppressing their male organisations and calling into play the 

 female ones, which they possess in a latent condition. In 

 further support of this view, Orton has shown that in the mollusc 

 Crepidula fornicata also the males under certain conditions may 

 change into females, thus showing that they have the poten- 

 tialities of both sexes. 3 



Further evidence in support of the view that each sex is latent 

 in the other is afforded by the well-known fact that the characters 

 of one sex can be transmitted through the other. For example, 

 Darwin states that the gamecock can transmit his superiority 

 in courage and vigour through his female offspring to his male 

 grandchildren, while with Man it is believed that diseases such 

 as hydrocele, which are necessarily restricted to the male sex, 

 can be handed on through female children to a future generation. 4 

 Again, it is well known to cattle-breeders that a bull which is 

 descended from a good milking stock can transmit this quality 

 to his female offspring. 



Smith has laid much stress on the relation between sex and 

 metabolism, inasmuch as changes in the latter are capable under 

 certain circumstances of calling forth the characters of the 



1 Potts, " The Modification of the Sexual Characters of the Hermit Crab 

 caused by the Parasite Peltogaster" Quar. Jour. Micr. Science, vol. 1. 

 1906. (See p. 308, Chapter IX.) 



2 Smith (G.), "Sex in the Crustacea," &c., British Association Report, 

 Leicester Meeting, 1907 ; " Studies in the Experimental Analysis of Sex," 

 Quar. Jour. Micr. Science, vols. liv. and lv., 1910. (See p. i;.",*., 



3 Orton, "On the Occurrence of Protandric Hermaphroditism in the 

 Mollusc Crepidula fornicata," Proc. Roy. Soc., B., vol. Ixxxi., 1909. 



4 Darwin, The Variation of Animals and Plants, vol. ii., Popular Edition, 

 London, 1905. 



