SEX-DIFFERENTIATION IN XIPHOPHORUS HELLERI. 71 



In 1908 the same author reported three more cases of arrhenoidy, 

 all of which were Glarydichthys januarius. In all three the form 

 index was strictly female, while the gonopod was well advanced. 

 After one of them died it was examined microscopically and 

 showed total absence of a gonad, while the duct was typically 

 oviduct. It is clear that this particular fish was in a late retro- 

 gressive stage, when it is very difficult to isolate the epithelium of 

 the ovarian cavity. In one of the remaining two Philippi found 

 the following peculiarities : " Makroskopisch liess dieses 3, ausser- 

 lich in bezug and die grosse ganz als Weibschen erscheinende Tier 

 2 nicht miteinander verschmolzene milchweisse Hoden erkennen, 

 in deren einem 2 dottergelbe grosse Eier sich befanden und die 

 beide einem typischem Oviduct Aufsassen." 



Newman (1908) reported on a case in Fnnduliis majalis, which 

 he at the time called " A significant case of hermaphroditism in 

 fish." As the specimen had advanced toward maleness in mor- 

 phology and behavior during the period of observation, and as 

 F. majalis is decidedly bi-sexual, the case is apparently one of 

 sex-inversion. 



2. Sex-inversion in Other Vertebrates. 



The work by Brandt (1889) on birds is of considerable interest. 

 The name " arrhenoidie " was coined to replace " Hahnenfedrig- 

 keit." It deals mostly with the domestic fowl, but observations 

 on game birds, etc., are not uncommon. Birds that have laid eggs 

 and have otherwise appeared and acted like females have been 

 observed to assume the appearance and behavior of the male sex. 



* 



Such changes occur most commonly with senility, but this is not 

 necessary, for birds of one year of age are known to transform. 

 It has been noted that some abnormalities, such as a solid or blind 

 duct, occur, but there are many with no such apparent causes. 

 Cytologically various stages of disintegration of ovarian structures 

 and new formation of apparently testicular tissues go hand in hand. 

 The differentiation of seminiferous tubules first begins as solid 

 cords which luminate and may develop from one to several layers 

 of epithelium. Such tubules show signs of spermatogenesis ; no 

 spermatozoa, however, have been encountered. 



Work of somewhat similar character has been described bv Pearl 



