The “ Sexuality ” of the Mucorinece. 215 
THE “SEXUALITY” OF THE MUCORINE/E. 
I T has been known for some time that zygospores of some 
members of the Mucorineae, e.g., Sporodinia grandis, are of 
common occurrence and can be obtained in the laboratory with 
ease, while the zygospores of others are found less frequently and 
are obtainable by culture only with great difficulty. The occurrence 
of fruit-bodies in the latter forms was thus supposed to depend on 
some special external conditions, and various methods were proposed 
to ensure their production, but none of them proved certain in 
practice. 
The key to this mystery of zygospore production was discovered 
by Blakeslee a short time ago and the explanation was shown to be 
very simple, though entirely unexpected. In 1903 Blakeslee was 
working on the problem of zygospore formation in Mucor Mucedo 
and obtained pure, zygospore-producing, cultures on agar. It was 
found that cultures from single sporangia of this material never 
produced zygospores ; but if a mass of the mycelium was transferred 
as a whole, zygospores were produced in abundance around the 
point of inoculation, but they decreased in number as the growth 
widened. Again, it was found that mixed sporangial transfers from 
the centre of the mass gave origin to zygospores, while similar 
mixed cultures from the edge of the growth were unsuccessful. 
The culture which made clear the nature of zygospore production 
was prepared in order to discover whether the zygosporic activity 
could be transmitted through the mycelium derived from any single 
spore. For this purpose dilution cultures were made from mixed 
sporangial transfers from the centre of a zygosporic growth, resulting 
in one Petri dish which contained only five spores. When the five 
mycelia developed from these spores met, it was found that an 
abundant growth of zygospores occurred at the line of apposition 
of certain of the mycelia, while between others there was no such 
formation. Further, this culture showed that a certain mycelium 
might produce zygospores when meeting with a second mycelium* 
though it might be sterile towards a third mycelium, which itself 
was fertile with the second. The culture thus indicated that not 
only were two mycelia arising from different spores necessary for 
the production of zygospores, but also that these structures are 
only developed by the interaction of mycelia which are different 
in nature. 
