8APROL EONIA CB^. 



that the antheridia which fertilize one oogonium grow out 

 of the oogonium lying immediately beneath.* In this case 

 it appears that the terminal oogouium is formed first, and 

 that the antheridia, in each case, grow out from what is yet 

 a part of the whole filament, and that it is only subsequently 

 to the formation of antheridia that an oogonium is formed 

 out of that part of the filament out of which they grew. In 

 the accompanying diagram (Fig. 173) the ' 

 oogonium a is fertilized by antheridia 

 which grew out of that portion of the 

 filament which subsequently became cut 

 off as oogonium b, which in turn is fer- 

 tilized by antheridia from below it, and so 

 on to d, which receives its antheridia 

 from what still remains as part of the fil- 

 ament. Each oogonium is seen to be 

 younger than the one above it in other 

 words, the oogonia are developed from 

 the top of the filament downward. 



The oospores of Saprolegniaceae possess, 

 when mature, a thick integument, which 

 is double that is, formed of an outer 

 thicker coat (epispore) and an inner thin- of 

 nerone(endospore). After a considerable 



Fig. 173. Diagram il- 

 lustrating the formation 

 the sexual organs 



period of repose the oospores germinate wh^^Nfertiifzed"^ 



by sending out a tube, f 



The Saprolegniaceae have been but little stud- 0|jn e roo^oninm with 



ied in this country, although they may be read- the oocplieres not yet 



ily obtained. They grow quickly upon dead e " t ^xcmimn ; the U hu- 



fishes, crayfishes, flies, etc., when placed in tanks ter wilF be fertilized by 



of water, and may often be seen attached para- grow outfrom'fhe upper 



sitically to young living fishes in aquaria. They j-' nd of the filament be- 

 are often so abundant in the breeding-houses of 

 fishes as to cause great losses. In some of the rivers in England dur- 



* The student should consult, an article on " Two New Species of 

 Saprolegniese," etc., in Qr. Jour. Mic. Science, 1867, p 121, in which 

 figures and a description of such a form as that above referred to are 

 given. 



f See De Bary's" Morphologic und Physiologic derPilze," etc., 1866, 

 p. 155, for an account of the sexual reproduction of Saprolegniaceae, 



