in the Pseudopodia of the Rhizopoda. 405 



may here indicate especially that the quiescent filaments allow 

 themselves to be readily curved into any form by others which 

 are moving, and then remain in this form until they are brought 

 out of it by their own movements or those of other filaments. 



During the mutual displacements of the filaments, and the mu- 

 tual approximation thereby often produced, another remarkable 

 property shows itself, — namely, their ready adhesion to each 

 other. In consequence of this ready adhesion, it happens that 

 the filaments very commonly issue from the shell in larger or 

 smaller bundles, and only subsequently separate. It is also 

 frequently observed that a filament which has, in consequence 

 of its own movement, got under others and then become quies- 

 cent, clings to other moving filaments during their passage, and 

 is carried forward passively with them, not unfrequently like an 

 anastomosis between them. 



Phenomena of active Movement in the individual Pseudopodia 

 of the Polythalamia. 



To the phenomena of active movement in the pseudopodia of 

 the Polythalamia I refer — 



1. The issuing of the filaments from the shell, their extension 

 and retraction. 



If the filamentous pseudopodia, which are originally mor- 

 phologically simple, • could actually become converted into 

 branched forms, and the latter again revert to the original 

 form, this change of form must also have belonged to the 

 category of active movements ; but these changes of form, as 

 I shall afterwards prove, are either only apparent or not 

 capable of being established with certainty. 



2. A tortuous or vermiform movement, usually somewhat slug- 

 gish, of the more or less extended filament, either throughout 

 its whole length or in some section of it. 



3. The phenomenon described under the name of ff gi-anular 

 movement." 



4. A mutual displacement of the filaments, often occurring im- 

 perceptibly, by their closer approximation or removal to a 

 greater distance, or also by their separation from a bundle in 

 the general radiary complex, under circumstances which do 

 not allow the detection of the active movements of other fila- 

 ments as co-operating causes. To the changes in the arrange- 

 ment and form of the total radiary complex of filaments I would 

 not refer more particularly. In these changes, both active 

 movements of the filaments and passive ones caused by their 

 ready adhesion to each other, participate ; and it is often quite 

 impossible to calculate exactly the part taken by each kind of 



