INTRODUCTION. 25 
forms outside the shell-mouth of the parent, and this 
bud grows, until, having acquired a size approximate 
to that of the parent, a chitinous test is secreted, and 
the “bud” falls off and pursues an independent 
existence. Several “buds” may be formed by a single 
individual at the same time. 
Fig. 13.—Early stage in the conjugation of Diflugia pyriformis, 
var. lacustris: two individuals approaching each other, the 
plasma of the one enveloping the oral aperture of the other, 
and the granular substance of the two animals commingling. 
A few minutes sufficed to bring the mouths of the tests close 
together. x 200. 
The cysts, so commonly observed in the testaceous 
Rhizopoda (Nebelu, Difflugia, Englypha, etc.) protect 
what are known as “swarm-spores.” The parent 
organism splits up into separate cells, each cell pro- 
vided with its portion of the nucleus, and also, on 
liberation, with means of locomotion, which may be 
Fie. 14.—Late stage in the conjugation of Nebela collaris: two 
tests closely adhering, one filled with protoplasm, the other 
nearly empty. In the latter the remaining protoplasm con- 
tinued to be attached to its test by numerous protoplasmic 
threads. x 250. 
flagella or pseudopodia. These either undergo subse- 
quent fission or develop at once into the typical form. 
_Encistment is probably preceded by the conjugation 
(“copulation,” Blochmann) of two individuals. It has 
been observed in many testaceous forms. Individuals 
in pairs, having the mouths of their tests closely 
