930 The American Naturalist. [October, 
view that the formation of a plasmodium indicates a wide separa- 
tion in the natural position of the Myzxomecetes from the fungi, but 
he suppressed that name entirely, adopting De Bary’s class name 
in its place; at the same time, he admitted into his 
Monograph Dictyostelium, a genus of the Acrasiew. The reason for 
his including this genus may be the fact pointed out by De Bary, that 
Brefeld in first describing the dense aggregations of swarm-cells into 
the stalked spore-masses of Dictyostelium, refers to them as being “ plas- 
modia; that is, products of the coalescence of swarm-cells ;” and it was 
not until after the publication of Rostafinski’s Monograph that Van 
Tieghem in 1880 and Brefeld in 1884 corrected this view. Accepting 
the Mycetozoa as established by Rostafinski, but excluding Dictyostelium 
on the ground of its not forming a true plasmodium, we have a clearly 
defined group of organisms separated from all others by the following 
combination of characters.. A spore provided with a firm wall pro- 
duces on germination an amceboid swarm-cell which soon acquires a 
flagellum. The swarm-cells multiply by division and subsequently 
coalesce to form a plasmodium which exhibits a rhythmic streaming. 
The plasmodium gives rise to fruits which consist of supporting struct- 
ures and spores ; in the Endosporee these have the form of sporangia, 
each having a wall in which the free spores are developed. A capil- 
litium or system of threads forming a scaffolding among the spores is 
present in most genera. In the Exosporee the fruits consist of sporo- 
phores bearing numerous spores on their surface. 
The affinities of the Mycetozoa have been dealt with by de Bary and 
Zopf in the works before referred to. It had been suggested that they 
were allied to the fungi through the Chytridee, which do not always 
form a mycelium, and in which the entire vegetative body is finally 
transformed into a many spored sporangium, the vegetative body and 
spores having the power of amceboid movement for a longer or shorter 
time. ary, however, -mentions among other points of difference 
that the Chytridee do not form a plasmodium by the coalescence of 
swarm-cells, “and there is, therefore, no ground for assuming their 
direct relationship with the Mycetozoa. 
The position of the Acrasiee in which the swarm-cells exhibit 
amceboid movements, but do not produce a flagellum, and aggregate 
without coalesceing into a true plasmodium, has already been referred 
to. The view held by De Bary that the Mycetozoa are more closely 
associated with the Protozoa is supported by a comparison with the 
pelagic Protomyxa of Heckel, which is stated to develope a plasmodium 
by the coalescence of swarm-spores, and differs from the Mycetozoa 
