to 1000 females 



SPECIAL CASES OF SEX-INHERITANCE 225 



dinary perversions of the sex ratios. The table gives 

 the ratios that Maupas discovered. Not only are the 



Diplogaster robustus 0.13 male 



Rhabditis guignardi 0. 15 male 



Rhabditis dulichura 0.7 male 



Rhabditis caussaneli 1.4 males 



Rhabditis elyaus 1.5 males 



Rhabditis coronata 5.0 males 



Rhabditis perrieri 7.0 males 



Rhabditis marionii 7.6 males 



Rhabditis duthiersi 20.0 males 



Rhabditis viguieri 45.0 males 



males extremely rare — almost reaching a vanishing 

 point in certain cases — but they have lost the instinct 

 to fertilize the female. 



The females, on the other hand, have acquired the 

 power of producing sperm, so that they have passed 

 over into the hermaphroditic state. The behavior 

 and history of the sperm that the females produce has 

 only recently been made out by Miss Eva Kriiger. 

 It is found that a spermatozoon enters each egg and 

 starts the development, but takes no further part in 

 the development (Fig. 108). The egg may be said to 

 be half fertihzed. It is a parthenogenetic egg and 

 produces a female. 



(5) Some very high male ratios have been reported 

 by Guyer in cases where birds of very different families 

 have been crossed — the conimon fowl by the guinea 

 hen, individuals of different genera of pheasants bred 

 to each other and to fowls, etc. Hybrids between 

 different genera gave 74 ^ — 13 9 . Hybrids between 

 different species of the same genus 12$ — 18 9. In 

 most of these cases, as Guyer points out, the sex is 



