494 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
in Cambridge, it was readily mistaken for one of the latter genus. 
Notwithstanding the fact, however, that we may call the fructifying 
colonies of the Labyrinthuleae and the Acrasieae physiologically 
equivalent, when we come to compare the individuals of the two 
groups, we see no evident points of resemblance. The spindle 
shaped individuals, at least in Diploplirys stercorea and presumably 
in other members of the group, do not show the amoeboid move¬ 
ments and internal protoplasmic streaming of the myxamoebae, and 
they are flexible only to a slight degree. Moreover, in their nuclei 
and in the peculiar mode of division, the individuals do not resemble 
in the least those of the Acrasieae. In the peculiar, fine, elongated 
pseudopodia of Diplophrys, which are constantly borne at two 
definite points and which are not variable in form and origin as are 
those of the Amoebae, this organism shows close resemblances to 
the Reticulariidae rather than to the Amoebae with which Zopf 
associates the group. The individuals of the Labyrinthuleae, in 
their fusiform shape, in their internal structure, and in their oblique 
division, as well as in their peculiar mode of locomotion, clearly 
differ widely in character from the myxamoebae of the Acrasieae 
and of the Myxomycetes. It follows, therefore, that, although some 
« 
similarities are undoubtedly present between the fructifications of 
the Labyrinthuleae and those of certain simpler forms of the Acra¬ 
sieae, the likeness may be regarded as probably accidental and 
confined to external resemblances only. 
In searching for undoubted affinities of the Acrasieae, de Bary 
has pointed out that we are led by a very short step to the Amoe¬ 
bae. The latter are organisms which have the amoeboid movements 
of the myxamoebae, which multiply similarly by successive division, 
but which do not form aggregations in any way. They may pass 
singly and without aggregation into encysted states, which are simi¬ 
lar in all respects to microcysts and which do not essentially differ 
from the spores of the higher Acrasieae. Indeed, in Sappinia we 
have a naked amoeba which undergoes encystment either singly or 
in occasional aggregations at the ends of projections above the sur¬ 
face of the substratum. It thus essentially differs from Guttulinopsis 
only in the fact that the colonies of myxamoebae of the latter aggre¬ 
gate in response to some chemotactic stimulus. We may readily 
believe that the pseudoplasmodium of the Acrasieae may have arisen 
from forms which had habits similar to those of Sappinia, and that 
