588 Wager . — The Sexuality of the Fungi. 
maintaining the existence of the species under circumstances 
which are unfavourable to the vegetative existence of the 
individual.’ 
The number of cases in which there is a blending of two 
distinct lines of descent into one is rare, and sometimes the 
conjugating cells are closely related to one another. In 
Basidiobolus the fusion always takes place between adjacent 
cells. In the Peronosporeae the same filament often gives rise 
both to the male and female organs, and in some cases this 
appears to be the rule. In Mucorineae the conjugating cells 
are borne on separate filaments, but these may be, and often 
are, branches of the same plant. In Polyphagus Euglenae two 
distinct individuals fuse together, but in Zygochytrium the 
conjugating cells are produced on different filaments proceed- 
ing from the same individual. Thus so far as sexual 
differentiation is concerned, all we can say is that although the 
conjugating nuclei are in most cases removed at some distance 
from one another in their development, yet the required 
stimulus may be obtained when they are as closely related as 
in Basidiobolus. 
It has been shown that the need for fertilization in the 
simpler forms of Fungi and Algae depends to a certain 
extent upon external conditions, which affect transpiration, 
atmospheric pressure, and food supply. The connexion 
between food supply and sexuality in the Fungi was 
suggested by Marshall Ward 1 in 1884 ; and Eidam 2 showed 
that if the conidia of Basidiobolus are sown in a nutrient fluid, 
a firm mycelium is produced, which forms simultaneously both 
asexual and sexual cells. In an exhausted nutrient medium, 
on the contrary, the conidia produce only a loose mycelium, 
which immediately and exclusively gives rise to sexual cells, 
which unite together to form zygotes. 
Again, Raciborski 3 , in 1896, working with the same Fungus, 
1 H. Marshall Ward, On the Sexuality of the Fungi. Q. J. M. S., vol. xxiv, 
1884. 2 Loc. cit. 
3 Raciborski, Ueber den Einfluss ausserer Bedingungen auf die Wachsthumsweise 
des Basidiobolus ranarum. Flora, 1896, p. 107. 
