OF THE PROTOZOA. EHIZOrODA. 207 



Dujardin made some precise observations respecting the characters of the 

 locomotive variable processes and the rate of movement. In Gromia oviformis, 

 he describes a filament to begin as a very fine simple and imiform offshoot, 

 which elongates and directs itself in different directions, in order to seek a 

 point of attachment ; sometimes it oscillates, at others it exhibits a tolerably 

 rapid nndiilatory movement, or, otherwise, it rolls itself up in a spiral manner, 

 when the several coils coalesce, and a mass is formed capable of throwing out 

 afresh other processes. Proportionately to the extension of the filament, its 

 substance is added to by an afliux of new substance from the chief mass, evi- 

 denced by the movement of irregular granules, which give the fibres an un- 

 equal and nodose appearance. Moreover, the fibre gives off branches here and 

 there at a more or less acute angle, which, in theii' tui-n, ramify after the same 

 fashion, and establish communications or anastomoses with one another. Often 

 also films or laminte of the gelatinous substance form at the extremities of 

 contiguous fibres, which extend themselves variously. The filaments retreat 

 by an inverse movement ; and this is occasionally so sudden that the end as- 

 sumes a button-like termination from the fusion of the mass of matter engaged 

 in its formation. 



The expansions of M'dlola, he fiu'ther tells us, are six times finer than those 

 of Gromia, and the movement of the animal more rapid ; for during summer 

 it moves from about -^^ih to ^th of an inch in an hoiu-. CristeUaria moves -J-th 

 of an inch, and Vorticicdis from -^th to -^rd of an inch in a like period. 



The variable processes also constitute the prehensile organs of the Rhizo- 

 poda. Any small objects serviceable for nutrition, with which they come into 

 contact, are laid hold of by them apparently by means of their viscid surface ; 

 and, except they are animalcules of considerable size and power, they are un- 

 able to escape. When a filament or, as we may call it ^vith reference to this 

 function, a tentacle has so seized its prey, adjoining fibres aggregate about 

 it and coalesce, a current of the viscous substance sets in towards the spot, 

 and very soon envelopes the object by a fJm. The prey being thus secured, 

 the processes shorten themselves and di^aw it towards the chief mass or body 

 of the animal, or, otherwise, the object seized continues in the same i>lace, and 

 the whole organic substance moves towards it, — the result being in either case 

 that it is engulfed. In the Amoehina this prehensile act proceeds as just 

 stated; in the Monothalamia and in those Foraminifera having a large 

 opening in the last chamber, the body seized is directed to the large orifice 

 of the shell ; but in those having no other than fine pores or minute fissures, 

 it would not seem to reach the general mass, but to be used up for the jDur- 

 poses of nutrition externally to the shell, by a digestive action inherent in 

 the fibres themselves. The mode of entrance, therefore, of food within the 

 Aiscid organic matter, is not so simple and mechanical an act as Dujardin re- 

 presented it, but has much mxore of a vital character. This observer's state- 

 ment was, that the mere pressure of the body of the animal on the smface it 

 moved over caused the penetration of foreign matters, which, by subsequent 

 extensions and contractions of different parts of the substance, became at 

 length completely involved in it. It would seem that animalcules may swim 

 about unharmed within the meshes of the sarcode-web, but that so soon as 

 they touch one of its fibres, they are as it were paralysed and incapable of 

 further motion, and are consequently dra^^m deeper into the net without any 

 opposition. Sehultze, who has noticed this circumstance, believes it to be 

 quite exphcable as a simple mechanical act, and no proof of a special be- 

 numbing property resident in the soft substance as Ehrenberg was inclined 

 to suppose. Food, or indeed any extraneous matters, may enter the soft 

 bodies of Rhizopoda at any point of their surface ; ?. e. in other words, those 



