659 
on species of Tolypothrix. 
or two hyphae in various directions (Figs. 5 and 9), relatively 
only a few of which are successful in penetrating an algal 
filament. Fig. 5 shows a spore which has rather thicker walls 
than is usual in this species ; such spores are occasionally 
to be found. 
As already mentioned, this mode of formation of the spores 
does not account for their occasional position within the 
layers of the Tolypothrix-shediXh (Fig. 1). Such a position 
can be accounted for by assuming spore-formation to have 
taken place on a mycelial branch, ramifying in the sheath of 
the Alga. Such mycelial branches undoubtedly occur, but 
I have never observed a formation of spores in them. 
In a few individuals certain parts of the parasitic hyphae were 
seen to be very much more swollen than others (Fig. 18); 
such swollen portions may possibly develop into internal 
spores, analogous to those of R. nodosa , Dang., but I have 
as yet been unsuccessful in following up their further fate. 
They were especially observed in material grown in a solution 
of cane-sugar. Since the spores usually formed by R. Boodlei 
are relatively thin-walled and incapable of existing for a long 
period, it would seem natural that they should only be formed 
on the external and not on the internal mycelium. For 
spores, formed in this latter position, must be surrounded for 
a long time by the empty sheath of the Tolypothrix , and 
months would ordinarily elapse before this latter would decay 
and leave the spores lying freely in the water. It is true 
that the fungal hyphae normally have to penetrate the sheath 
of the Alga, but it is questionable whether a young, just- 
formed hypha is capable of doing this. 
I have had the species described under observation for 
several months, and have seen no indication of zoospore- 
formation. 
The life-cycle of R. Boodlei may be briefly summarized as 
follows : Mycelial branches, emerging from the internal 
parasitic hyphae, give rise to large numbers of thin-walled 
spores. These germinate almost at once, giving rise to one 
or more hyphae, which attack the host and penetrate into 
