262 D. D. CUNNINGHAM. 
division ;! we find that it is impossible to distinguish between 
resting zoospores and bodies which pass on into an ameeboid 
state; and we know that the zoospores merely differ from 
Ameebee in the character of the protrusions which they emit, and 
therefore in the nature of their movements. Allowing the 
identity of the two forms, we have a ready means of accounting 
for the regularity and abundance of the crops of sporangia and 
the general ratio of these to the numbers of zoospores, while 
rejecting it we have no explanation to give of the appearance of 
the multitudinous development of ameeboid bodies. 
In the endeavour to obtain more positive evidence on this 
point, hundreds of cultivations on a small scale were carried 
out with more or less satisfactory results. In some cases there 
appeared to be no doubt that the zoospores originally present 
became converted into Amcebe at a later period, but the 
difficulty of attaining to absolutely certain results appears to be 
almost insurmountable. In the first place, in order to render 
any such cultivation susceptible of continuous observation, it is 
necessary to introduce conditions which we have already found 
to exert a most prejudicial effect on the vitality of the zoospores, 
for the basis must necessarily be diluted with some fluid in 
order to render the organisms visible. A condition of fluidity 
of the basis, too, independent of any actually destructive effects, 
certainly influences the occurrence of developmental processes 
in other ways. ‘The persistence of zoospore forms may be pro- 
longed, and the appearance of amceboid ones be delayed by an 
excess of moisture as may readily be proved by experiment. So 
again an excess of fluidity in the medium seems to be one of 
the agencies capable of causing ameeboid bodies present in it to 
assume the encysted condition in place of passing on to the 
normal sporangic development. Another great obstacle to the 
satisfactory decision of this question lies in the excessive and 
constant movement of the zoospores, which renders it impossible 
to secure any individual specimen for continuous observation 
over a prolonged period. 
All that can be positively affirmed is that the ameeboid bodies 
which replace the zoospores primarily present appear to be 
directly derived from the latter, and that the two forms seem 
merely to represent different developmental stages of one and 
the same organism, connected with one another by the interven- 
tion of an inactive stage. 
The Amcebe, when they first appear, are of very minute size, 
ranging from 5 » to 7 « and upwards in diameter when ina 
spherical condition (Pl. XVIII, fig. 1). In some cases a 
1 Processes of division have been observed to recur in one body twice in 
the course of an hour. 
