OLIVE : MONOGRAPH OF THE ACRASIEAE. 
453 
ing its activity under favorable conditions by the formation of a 
small plasmodium. 
After a more or less definite period, during which the plasmodium 
vegetates as a unit and increases greatly in size, it ceases to 
appropriate further nourishment, begins to reject such foreign 
material as it may contain, and becomes more or less heaped up, or 
‘‘ aggregated.” This aggregation marks the beginning of the fructi¬ 
fying period which ends with the formation of highly differentiated 
sporangia or sporophores, having various habit, and bearing well 
defined spores, each provided with one or more walls which are, in 
some cases at least, composed of cellulose. 
The life history of the Myxomycetes is thus clearly separable into 
two main periods — one of vegetation and one of fructification — in 
each of which two secondary periods may be distinguished. In the 
first instance, a period of active existence and of multiplication in 
the swarm cell and in the single amoeboid condition, is followed by 
a state in which the coalescence of individual amoebae and small 
plasmodia combines wHh continued active growth and nuclear divi¬ 
sion to increase enormously the number of potential individuals of 
the vegetative mass. In the second instance, the completion of the 
vegetative period is followed by one of aggregation which is a prepa¬ 
ration for the final condition of fructification. 
In the order Labyrinthuleae, are grouped a small number of para¬ 
sitic and saprophytic organisms, embracing but five species in two 
genera, which are included by some writers among the Protozoa. 
In their developmental history, encysted cells in some cases, or spores 
in others, on reassuming the vegetative state, give rise to from one 
to four spindle shaped cells, each of which possesses in its active 
condition two radiating tufts of pseudopodia, borne at nearly 
opposite poles. These cells may remain separate, each retaining 
complete individuality, or, as more often happens, as they lie adja¬ 
cent, their pseudopodia may adhere to or anastomose with those of 
other cells, thus forming by partial fusion or by contact the peculiar 
type of association which Zopf has designated as a ‘^net-plasmodium.” 
During this vegetative condition, the fusiform individuals, each 
showing a limited degree of contractility, appear to glide along the 
filamentous pseudopodia or fibrous framework thus produced, being 
evidently thus directed and limited in their wandering. During the 
active state, the individuals increase in size by the absorption of 
nourishment and reproduce by division. 
