492 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
it appears unlikely that the Myxomycetes have been derived directly 
from the simpler organisms, since they have in reality but one fea¬ 
ture which is strictly comparable, namely, the amoeboid stage of 
their existence. 
The plasmodium is evidently not at all analogous to the pseudo- 
plasmodium, as Zopf (’ 92 ) and others have pointed out, for the 
aggregation in the latter case is not a vegetative mass as is the 
plasmodium, but is simply a heaping up of individuals for the pur- 
jDOse of forming a fructifying body, and it therefore follows the 
vegetative stage. Moreover, the vegetating plasmodium, as Harper 
has suggested, although a product of cell fusions without nuclear 
fusion, is in its nutrition, reactions to stimuli, and growth, a physio¬ 
logical unit, just as a myxamoeba is a unit. On the other hand, 
the pseudoplasmodium, although responding as one mass to certain 
stimuli, it is true, is not in the least -a unit, since the individuality 
of each member of the colony is preserved throughout the develop¬ 
ment of the pseudoplasmodium to a sporiferous body. Further¬ 
more, the nuclei of the jDlasmodium multiply greatly during its 
nutritive stage, (Lister, ’ 93 ) as well as again during the preliminary 
fructifying stage (Strasburger, ’84 ; Lister, ’93 ; Harper, : 00 ), thus 
increasing enormously the number of potential individuals. On the 
other hand, the individuals of the pseudoplasmodium of the Acra- 
sieae do not increase in numbers nor are there nuclear changes 
therein. 
Although that period in the development of the plasmodium 
which may be termed the period of aggregation, during which the 
protoplasm heaps up preparatory to fructification, is comparable 
physiologically with the pseudoplasmodium, the structural differences 
between the two at this time are very apparent. In fact, it becomes 
evident on careful comparison throughout their development, that 
the only strictly comparable portion, structurally, in the two groups 
is, as mentioned above, the amoeboid stage of their existence, 
since the life cycle of the Acrasieae includes neither the swarm cell 
nor the plasmodium condition of the more highly differentiated 
order, while the sporophores of the two, furthermore^ show little 
resemblance. We may, however, see some likeness perhaps in the 
stalk of Stemonitis, in that it is formed somewhat similarly, as a 
central supporting column, but neither the main stalk nor the capil- 
litium in this case is protoplasmic in nature. Again, some members 
