PERSONAL VIEWS ON PHYLOGENY 185 



no apparent sexual differentiation between the two gametes, 

 and no receptive cell in the sense of a previously destined 

 oogonium. Under the circumstances, either gametes 

 originated as a modification of antheridium and oogonium 

 respectively, or the conjugation by gametes was a new 

 creation on the part of some of the Phycomycetes. Of 

 course it may be suggested that the Zygosporeae are 

 descended from algae like Zygnema. The whole question 

 turns on this point. Is it possible for the same apparent 

 type of sexual reproduction to appear at different periods 

 of time, and in different groups of organisms, without im- 

 plying phylogenetic affinity ; or does the second appearance 

 of a given type of sexual reproduction always imply 

 phylogenetic affinity with the organisms furnished with an 

 apparently similar type at a previous period? If phylo- 

 genetic affinity is implied, then we have indicated two, or 

 probably three, independent origins from the algae in the 

 group of fungi we call Phycomycetes alone. The Oomy- 

 cetes would come from the Vaucheriae, and the Zygomy- 

 cetes from Zygnemae. As to whether the sexual act in 

 Polyphagus conforms with either of the above, is not 

 certain. 



Now in the Oomycetes, the most primitive group of 

 fungi, we find the ancestral form of sexual reproduction by 

 antheridia and oogonia, and the asexual method by means 

 of motile zoospores. In this same group the conidial or 

 asexual generation has gradually increased in complexity, 

 and the original zoospore-producing fruit has changed to a 

 body germinating by means of germ-tubes or hyphae. 



Coming to the next group, the Mucorineae, we find the 

 sexual reproductive bodies to be gametes, and the result of 

 the sexual act a zygospore. Again, if phylogenetic affinity is 



