564 



GENERAL PHYSIOLOGY 



With their decomposition the surface-tension would increase, and 

 the stimulated protoplasm would necessarily flow back centripetally, 

 so that the pseudopodia would be retracted a phenomenon that 

 is called out in a very characteristic manner by all sorts of stimuli. 

 Thus the phase of contraction would be mechanically explained. 

 After their return to the central cell-body the biogen-molecules 

 would have an opportunity to regenerate themselves with the aid 

 of substances produced by the protoplasm and the nucleus, which 

 are absolutely necessary to the intact life of the cell ; then after 

 the introduction of oxygen they would begin their course anew. 



In accordance with this idea, all the special phenomena exhibited 

 by amoeboid protoplasmic masses in their movement may be 

 understood. The necrobiotic phenomena of naked protoplasmic 

 masses especially, which can be followed very beautifully in 

 amputated, non-nucleated, hyaline pseudopodia of Difflugia 



FIG. 270. Difflugia lobostoma, with two pseudopodia projecting from the sand-capsule, the larger 

 of which is amputated. Beside it, the changes which the separated mass of protoplasm passes 

 through in the course of a few hours are shown from the left above to the right below. At 

 first, normal movement with formation of pseudopodia, finally, death in the spherical form. 



(Fig. 270), may be explained at once : the continuation of the 

 amoeboid motion at the beginning, the gradual cessation of the 

 formation of pseudopodia, and finally death in the spherical, con- 

 tracted condition. 1 At the beginning, immediately after the 

 amputation of the mass, a quantity of nuclear and protoplasmic 

 substances, which the biogen-molecules need for their regeneration, 

 is available in the protoplasm ; the extension and amalgamation of 

 the pseudopodia proceed at first normally. But gradually these 

 substances are consumed, the oxydized biogen-molecules become 

 decomposed, the pseudopodia retract, the regeneration of the biogens 

 becomes impossible, and the incomplete biogen-residues are in- 

 capable of oxidation. Hence new pseudopodia are no longer 

 formed, and, when all the oxidized molecules are decomposed, the 

 mass perishes without any further change of its spherical form. 



1 Cf. p. 327. 



