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 Dijflugia 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 

 Khizopoda (Nebela, Diffiugia, Euglyplia, 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 



FIG. 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. 



fiagella 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 



