CH. VIIL—MORPHOLOGY AND COURSE OF DEVELOPMENT.—AFFINITIES. 443 
form plasmodia by coalescence of swarm-cells and the Acrasieae which do not 
form plasmodia. The two groups are evidently closely related to one another, the 
only important difference between them being the coalescence of swarm-cells in the 
one group and their firm aggregation only in the other. It is easy to conceive 
that the one form of development has proceeded directly from the other, either 
the Myxomycete form from that of the evidently more simply Acrasieae, or in 
the converse order. 
The group of the Mycetozoa differs distinctly from the Fungi which have been 
the subject of the first part of this book in all such characteristics as do not belong 
to all organisms alike, and the descriptions already given of both kinds of plants 
render any further explanation of the point unnecessary ; their connection also with 
other known plants is still more remote. The difference would not be less decided, 
if the Mycetozoa were without their remarkable amoeboid movements, for such 
movements are observed in other vegetable cells which have not a firm membrane. 
The characteristic mark of separation lies in the formation of plasmodia or 
aggregation of swarm-cells. 
It is obvious moreover according to our present knowledge that the Mycetozoa 
are the superior terminal member or the two terminal members of a series of forms 
or developments which commence elsewhere. The most highly differentiated sections 
of the group, the Calcareae, Trichiae, Lycogala and others, give evidence of no close 
affinity with any more highly differentiated group; in other words, like the Gastro- 
mycetes with which they were classed by earlier botanists, they do not connect with 
any group above them. Hence in enquiring after their affinities we must be content 
with searching for a possible connection with an inferior group, and for the simpler 
forms from which they have proceeded. 
When we seek for such a connection among the forms with which we are 
acquainted, we find it impossible to establish any strict homologies, and we are 
limited to the observation of resemblances in form, structure and mode of life. Sucha 
course of unprejudiced comparison leads us by a very short step to the naked 
‘ Amoebae’ of the zoologists, especially in Biitschli’s sense, as the starting point,— 
organisms with bodies having the amoeboid movements of the swarm-cells of the 
Myxomycetes, which multiply, as far as we at present know, by successive bipartitions 
without forming plasmodia, and which may pass singly and without aggregation or 
coalescence into states of rest not essentially different in their characteristics from those 
of the spores of the Myxomycetes. Guttulina is really a naked Amoeba of this kind, 
and is distinguished from other known forms only by the aggregation of its spores. 
Guttulina protea, mentioned above as forming solitary spores, differs in this respect from 
the Amoebae ; it may be classed as well with the naked Amoebae as with the Acrasieae, 
and forms therefore a perfect connecting link with the Amoebae. Thus on the one hand 
the more highly differentiated Acrasieae join on at once to Guttulina, and on the other 
a short step further brings us to the type of Myxomycetes which form plasmodia, in 
which coalescence of swarm-cells into a plasmodium and redivision of the plasmodium 
into spores take the place of their aggregation. Forms like Guttulina may have 
developed phylogenetically in two divergent directions, on the one hand into the more 

1 Bronn’s Thierreich, see below, page 454. 
