PHYCOMYCETES 29 



segregated long ago by Fisch (p. 75) under the generic name 

 Reesia, though the gametes are cihate, the zygote is finally non- 

 ciliate and amoeboid. Such forms may be regarded, perhaps, 

 as representing transition conditions from the more primitive 

 type of sexuality where the fusing cells are ciliate to the more 

 recent types in which they are wholly non-motile. 



Planogamic copulation between cells dissimilar in size and 

 shape was unknown in the fungi until very recently, when it was 

 discovered by Kniep (p. 132) in Allomyces javanicus of the 

 Blastocladiaceae. In this species unicihate gametes, differing 

 considerably and constantly in size, fuse to form a biciliate 

 zygote. The zygote swims for a time, but soon invests itself in 

 a membrane, and puts out a germ tube which develops directly 

 into the rhizoid system comprising the young thallus. This 

 species in addition to being heterogamic (anisogamic) is also 

 heterogametangic. The gametangia, though of essentially the 

 same form, are of two sizes. The smaller always contains the 

 smaller gametes, while the larger contains the larger ones. 

 Influenced by the situation in other higher Phycomycetes, 

 Kniep regards the smaller gametangium as male and the larger 

 as female, and designates the two as antheridium and oogonium 

 respectively. As the larger gametes are formed in the larger 

 gametangium, it must be admitted that the only criteria avail- 

 able for a determination of the sexual identity of these structures 

 indicate that they are female. Nevertheless, the possibility 

 remains that they are not. Though isogamic-heterogametangic 

 or heterogamic-isogametangic members of the Phycomycetes 

 with planogamic copulation have not been discovered, it is clear 

 that the determination of sexual identity on the basis of size 

 alone would be even more questionable in such cases. It is 

 possible, moreover, that heterogamic-heterogametangic species 

 with planogamic copulation may be found in which the smaller 

 gametes are borne in the larger gametangium and the larger 

 gametes in the smaller. Even admitting that these hypothetical 

 types may be, in fact, wholly absent in the group it will be 

 agreed that every effort should be made to attain uniformity 

 and precision in the application of terms. To this end the 

 writer prefers to avoid the use of the names oogonium and 

 antheridium in this lower form in which both gametes are motile. 

 If the larger gamete in Allomyces javanicus be admitted to be the 

 female then the type of sexuality existing in this isolated case 



