Origin of Sexuality 285 



and often adjacent tube grows out as an antheridiuni, and 

 fuses with a larger spherical swelling, the oogonium. The 

 numerous spermatozoids of the former are then discharged 

 into the four to eight eggs formed inside the latter. But the 

 careful studies and experiments of the past quarter century 

 have demonstrated that not a few of the Saprolegniese which 

 evHidently had such sexual differentiation have gradually lost 

 it, so that parthenogenetic development of the egg cells occurs. 



In this connection, and also as shedding a striking light 

 on the whole question of sexuality, are Klebs's exhaustive 

 studies on Saprolegnia mixta (110: 513). He has shown that, 

 when cultivated on pure gelatine, the plant can give rise to 

 an active vegetative growth, but forms no reproductive bod- 

 ies. Change into pure water starts the formation of zoospor- 

 angia and setting free of zoospores. Abundant growth, as 

 well as zoospore formation, occur when the fungus is culti- 

 vated on agar albumen in running water. In a rather strong 

 solution of htemoglobin (^/2o to ^/io%) or in leucin solution, 

 growth with subsequent formation of sex cells occurs. On 

 dead insects or flesh extract in water, growth with subsequent 

 zoospore formation and succeeding sex cell formation take 

 place. In water with fibrin or syntonin added, growth with 

 simultaneous development of zoosporangia and sex cells is 

 observed. Finally actively vegetating material, when brought 

 into a ^/ioo% haemoglobin solution forms sex cells and sub- 

 sequently zoosporangia. 



Amongst the higher divisions of the Fungi the sexual process 

 is often so greatly reduced or condensed, in other cases appar- 

 ently so entirely obliterated, as to render exact comparison 

 TN-ith lower or higher groups difficult. But the \dew now fre- 

 quently accepted, that such condensation or obliteration is 

 largely due to the rich and complex organic material in which 

 they often live, having furnished the needed energizing stim- 

 ulus that ordinarily is yielded by gamete fusion, has much 

 in its favor. It would be beyond the scope of this work how- 

 ever to follow the intricate ramifications of asexual and sexual 

 modification in the Fungi. 



