BHIZOPODA RADIOLARIA : ACTINOPHRYS. 441 



delicate membranous wall, as shown at o. It has been stated by 

 various observers that the cavity of this sacculus is not closed, 

 externally, but communicates with the surrounding medium ; and 

 this appears to the Author to have been fully established by the 

 careful observations of Dr. Zenker. * There does not seem to be 

 auy distinct and permanent orifice ; but the membraniform wall 

 gives way when the vesicle contracts, and then closes-over again. 

 This alternating action seems to serve a respiratory purpose, the 

 water thus taken in and expelled being distributed through a 

 system of channels and vacuoles excavated in the substance of the 

 body ; some of the vacuoles which are nearest the surface being 

 observed to undergo distension when the vesicle contracts, and to 

 empty themselves gradually as it refills. The body of this animal 

 is nearly motionless, but it is supplied with nourishment by the 

 instrumentality of its pseudopodia ; its food being derived not 

 merely from Vegetable particles, but from various small Animals, 

 some of them (as the young of Entomostraca) possessing great 

 activity as well as a comparatively high organization. When any 

 of these happens to come into contact with one of the pseudopodia, 

 this usually retains it by adhesion ; but the mode in which the 

 particle thus taken captive is introduced into the body, differs 

 according to circumstances. When the prey is large and vigorous 

 enough to struggle to escape from its entanglement, it may usually 

 be observed that the neighbouring pseudopodia bend over and apply 

 themselves to it, so as to assist in holding it captive, and that it is 

 slowly drawn by their joint retraction towards the body of its 

 captor. Any small particle not capable of offering active resist- 

 ance, on the other hand, may be seen after a little time to glide 

 towards the central body along the edge of the pseudopodium, 

 without any visible movement of the latter, much in the same 

 manner as in Gromia. When in either of these modes the food 

 has been brought to the surface of the body, this extends over it 

 on either side a prolongation of its own sarcode-substance ; and 

 thus a marked prominence is formed (Fig. 233, c) which gradually 

 subsides as the food is drawn more completely into the interior. 

 The struggles of the larger Animals, and the ciliary action of Infu- 

 soria and Hot if era, may sometimes be observed to continue even 

 after they have been thus received into the body ; but these move- 

 ments at last cease, and the process of digestion begins. The 

 alimentary substance is received into one of the vacuoles of the 

 Endosarc, where it lies in the first instance surrounded by liquid ; 

 and its nutritive portion is gradually converted into an undis- 

 tinguishable gelatinous mass, which becomes incorporated with the 

 material of the sarcode-body, as may be seen by the general diffu- 

 sion of any colouring particles it may contain. Several vacuoles 



* See "Schultze's Arch. f. Mikrosk. Anatomie," Bd. ii., p. 332; and 

 "Quart. Joum. of Microsc. Science," Vol. vii., N.S. (1867), p. 263. 



