496 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
swarm spores, or occasionally a vegetative body which shows amoe- I 
boid movements, show characters which are similar in some respects .1 
to those of the Mycetozoa. Furthermore, as Harper (:00) has 'I 
pointed out, the method of formation of spores in the sporangia of I 
Myxomycetes by progressive cleavage, points to another similarity I 
to the Fungi, since the phenomenon is similar to that observed in 1 
the sporangia of Synchytrium, Pilobolus, and other members of the I 
group. I 
As pointed out by Dr. Thaxter (’ 92 ), there is also in the life his- I 
tory of the Myxohacteriaceae a phenomenon which presents a cer- I 
tain striking resemblance to the Acrasieae. These organisms are I 
distinguished from other bacteria in having two definitely recurring I 
periods in their life cycle — “one of vegetation, the other of fructi- I 
fication or pseudo-fructification through the simultaneous and con- I 
certed action of numerous individuals.” During the vegetative | 
stage, the rods lie separate. Through some contagious impulse, I 
they concentrate toward central points, by means of oscillating I 
motions, pile up one on another and become either gradually changed 1 
into rounded spores, as in one group, or else encysted en masse. I 
In Myxococcus, the spores are heaped in stalked or sessile sori and 1 
the fructifications resemble those of Guttulinopsis and Guttulina. In I 
the more complicated forms of the Myxohacteriaceae in which I 
pseudocysts are produced, the fructifications show little external i 
resemblance, it is true, to those of the Acrasieae, yet one may read- ^ 
ily compare the encysted masses of but slightly modified rods which | 
are enclosed in mucus, to the microcyst aggregations of Guttulinopsis, | 
since in both cases little modified individuals are held en masse by | 
a mucous substance. j 
1 
Especially does the possession of the physiological equivalent, the 
aggregation of bacteria, or “pseudoplasmodium,” recall at once the | 
Acrasieae. De Bary considered the aggregation of myxamoebae j 
in the lower order and the fusion into plasmodia in the higher organ- I 
isms, as the crucial marks separating the Mycetozoa from all other :j 
forms. In this group of bacteria, also, we have another instance of ^ 
pseudoplasmodium formation. But, as cautiously suggested by Dr. 
Thaxter, notwithstanding the fact that the general nature of the two 
corresponding periods in the Myxohacteriaceae and in the Acrasieae 
is in certain respects practically identical, the resemblance may be 
purely accidental, since the cells of the two organisms appear to dif- 
fer so widely in character. 
