. The British freshwater Rhizopoda and Heliozoa. which is occupied throughout itsentire length with a thread of stiffened the Amvehie. changes of form are sometimes veryrapid. The production of pseudopodia, or rather thecontributing cause, has been a subject of- lively con-troversy. The theories of the early observers were as INTROnuCTTON. 11 fantastic as they were varied. ^ Contractile fibres served for a time to explain the phenomena of advanced the theory of pressure from was, he held, a push forward of the more fluidcontents by the posterior ectopla
. The British freshwater Rhizopoda and Heliozoa. which is occupied throughout itsentire length with a thread of stiffened the Amvehie. changes of form are sometimes veryrapid. The production of pseudopodia, or rather thecontributing cause, has been a subject of- lively con-troversy. The theories of the early observers were as INTROnuCTTON. 11 fantastic as they were varied. ^ Contractile fibres served for a time to explain the phenomena of advanced the theory of pressure from was, he held, a push forward of the more fluidcontents by the posterior ectoplasm, after the extrac-tion of water had given the latter a tougher consis-tency. The posterior extremity was drawn intothreads as the Amoeba advances, and the effect of areversal of the direction of movement, he said, was seenin a flow of ectoplasm from the posterior region, themore tenacious protoplasm appearing then on the oppo-site side.* Dr. Wallich disputed Grubers theory, and reiterateda view which he had long previously expressed, Fig. 4.—Anastomosing pseudopodia of Biomyxa vagans. x about 150. that the rush of granules is not dependent upon anyprevious contractile effort exercised in the posteriorregion. The flow merely takes the place of the ectosarcwhich has been suddenly projected forward. Hence, heargued, the motion is dependent on the contractile powerof the external sarcode layer, and the endosarc onlypassively participates in it. t Calkins sums up the controversy by remarking thatof late years, especially since Biitschlis masterly workon the structure of protoplasm, there has been a generaltendency to abandon the older theory of contractility,and to explain the movements of amoeboid bodiesthrough the physical laws of liquids, and in particularthe laws of surface-tension. The origin of a pseudo- * Zeitschr. fur Wiss. xl (1884). t Ann. and Mag. Nat. Hist. (5) xvi (1885), p. 215. 12 BRITISH FRESHWATER RHIZOPODA. podium is clearly in the ectoplasm, a
Size: 2689px × 930px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauth, bookcentury1900, bookdecade1900, bookidcu31924000623961
