THE GENETIC RELATIONSHIP OF PARASITES 1 25 
having arisen by a process of degeneration and reduction. It is not 
denied that there must have been ampHfication some time in order to 
attain the long-cycle condition but it is believed that this did not take 
place after those organisms became parasites. Undoubtedly the 
long-cycle forms represent the highest development but probably not 
the latest. As suggested in a foregoing paragraph there is much in 
favor of the parasitic fungi having passed through an intermediate 
saprophytic stage. Ultimately, of course, they must have come from 
independent ancestors. The existence of independent thallophytes 
and saprophytes showing well developed pleomorphy indicates that 
this feature is not one which can be considered as having any peculiar 
connection with the parasitic mode of life. The transition of complex 
pleomorphic forms into heteroecious parasites may not seem an easy 
step but is not more difficult to appreciate than the interpolation of 
one or two new stages, upon an entirely foreign host, into the life-cycle 
of a simple parasite. 
Since our present interpretation of the evolution of the higher 
plants is the rise of the sporophyte and the decline of the gametophyte 
much has been made of an analogical application to these parasites. 
It has been pointed out that those forms with the longest sporophytic 
stages must have arisen in a progressive way. While this is doubtless 
the case there is much doubt whether they have progressed as parasites 
and whether the present short-cycle forms can be looked upon as 
representing their ancestors. It should be pointed out that there has 
been no decline of the gametophyte unless it be in the loss of pycnia 
in some species. However, the only forms in which pycnia are known 
to be absent are short-cycle forms, which are according to the theory 
of ancestral nature. The pycnia are without doubt functionless today. 
It would be odd indeed if the gametophyte of the latest type in evolu- 
tionary history should always develop a useless structure not univer- 
sally known in its ancestral forms. Surely this is not in conformity 
with the higher plants. There has been much discussion over the 
interpretation of the pycnia in the rusts. The view that they represent 
vestigial male organs is highly plausible. Without much doubt they 
have not been functional since the parasitic adaptation. A former 
sexuality in which an Aecidium-like structure bore the female organs 
is now replaced by a somatic doubling conjugation in the myceUal 
mass below the spore-structure. The eventual disappearance of the 
pycnial stage might be anticipated in the latest forms. If this has 
