308 THE PHYSIOLOGY OF REPRODUCTION 



and in the total absence of the testis secondary sexual characters 

 of the female type are found in a large percentage of cases ; but 

 this change in the direction of the opposite sex may set in prior 

 to the complete disappearance of the testes. The change is 

 manifested in the appearance of the egg-bearing abdominal 

 sac appendages, which have no representatives in the male.' 

 Potts states that in the hermit crab infected by a similar Pelto- 

 gaster, the modifications of the male which occur are of the same 

 type, and are maintained after the atrophy of the testis, and 

 cannot be necessarily consequent on the presence of a secretion 

 of the testis.^ 



In both these cases it is suggested that the modifications 

 which take place are brought about independently by changes in 

 the general metabohsm. 



In the male common shore crab it was found that the testis 

 underwent very httle diminution after infection by Sacculina, 

 but that the male approximated to the female type. The change, 

 however, was less marked than in the cases referred to above, 

 in which parasitic castration was almost or quite complete.^ 



It would appear, therefore, that whereas many of the 

 secondary sexual characters are closely associated with the 

 presence of the genital glands, there are others which develop 

 independently of any influence from the organs of reproduction. 

 Brown-Sequard * seems to have been the first definitely to 

 put forward the view that the testis exercises its influence upon 

 the metabohsm through an internal secretion elaborated by it. 

 He based his conclusion to a large extent upon the beneficial 

 effects which he believed to accrue from the administration of 

 testicular extracts. These extracts were supposed to possess 

 invigorating properties, and could be usefully employed in cases 

 of deficiency of testicular substance, or in old age, when the 

 testes lose their functional activity. It is not unhkely that 



1 Smith (Geoffrey), " Rhizocephala, Fauna and Flora of the Gulf of Naples," 

 Monograph xa.ir., Berlin, 1906. 



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

 caused by the Parasite Peltogaster," Quar. Jour. Micr. Sci., vol. 1., 1906 ; and 

 "Some Phenomena Associated with Parasitism," Parasitology, vol. ii., 1909. 



3 Potts, " Observations on the Changes in the Common Shore Crab caused 

 by Sacculina," Proc. Comb. Phil. Soc, vol. xv., 1909. 



* Brown-Sequard, "Du R61e physiologique et th^rapeutique d'un Sue 

 extrait de Testioules," Arch, de Phys., 1889. 



