186 SECTIONAL ADDRESSES. 



every generalisation. No one would doubt that such saprophytes as the 

 Polyblepharidacese are truly algal, and Monoblepharis, though classified 

 as a fungus, is possibly allied to the filamentous green plants. 



It may be hazarded that the fungi as a whole have their origin, perhaps 

 a common origin, among the Protista, and that they form a line of evolution 

 parallel with those of animals and green plants, in some sense comparable 

 to both, butMerived from neither. 



Phycomycetes. 



The simplest members of the Phycomycetes show biciliate zoospores, 

 the cilia being lateral and oppositely directed ; in Olpidium?- and 

 Synchytrium^ sexual reproduction is achieved by the union in pairs of 

 zoospores which have been retarded in development by dry conditions, 

 while in Monochytrium Stevensianum^ the fusion of naked, uninucleate 

 amoebse has been described. 



Very early in the development of the fungi, however, appears a more 

 specialised process, and one which has established itself as characteristic 

 of the group. In Olpidiopsis^ the individual consists of a single, 

 multinucleate protoplast surrounded by a delicate wall ; two such 

 coenocytes of different size, if side by side in the same host cell, may fuse, 

 the contents of the smaller passing into the larger. Similar union is 

 accomplished in Zygwhizidium^ by means of a conjugation tube put out 

 by the smaller individual. In Polyphagus^ the individuals are uninucleate ; 

 here again the conjugation tube is formed by the smaller cell, but the 

 contents of this cell do not pass beyond the end of the tube, and are joined 

 there by those of the larger, so that the wall of the zygote is provided by 

 the smaller participant, which also develops the tube. 



I have called attention to this case because it emphasises the danger 

 of generalisation in respect of the sexual apparatus of the fungi. Apart 

 from the retarded zoospores of Olpidium and Synchytrium, the sperms of 

 Monoblepharis, and perhaps the oospheres of the Saprolegniacese and 

 their allies, gametes are unknown, and we have to consider the association 

 of walled gametangia. This renders useless our usual criteria of sexual 

 differentiation. The male gamete is defined as the smaller and more 

 active, the female as larger and stored with food, but there is nothing in 

 our experience of green plants to justify the assumption that the 

 antheridium need differ from the female organ either in size or activity. 

 Two criteria remain, the superior activity, not of the antheridium, but of 

 its contents, corresponding to the activity of the male cells in other plants 

 and animals, and the production of the zygote wall, characteristically a 

 function of the female cell or its environment. Bearing these characters 

 in mind, no difficulty arises among higher forms in distinguishing the 

 male and female gametangia. Polyphagus may be regarded as still in 

 the experimental stage in this respect. 



Among Oomycetes the contents of the oogonium may form a single, 

 multinucleate mass, into which enter numerous antheridial nuclei, or one 

 female nucleus only may be selected while the others disintegrate, or 

 several uninucleate masses may be formed, as in Saprolegnia, and each 

 be separately fertilised. In every case the conjugation tube is antheridial 



