On suction in Suctoria 



Mitchison, J. M. (1952). Cell membranes and cell division. Symp. Soc. exp. Biol. 6, 

 105-127. 



Noble, A. E. (1932). On Tokophrya lemnarum Stein (Suctoria) with an account of its 

 budding and conjugation. Univ. Calif. Publ. £ool. 37, 477-520. 



Pestel, B. (1931). Beitrage zur Morphologie und Biologie des Dendrocometes para- 

 doxus Stein. Arch Protistenk 75, 403-471. 



Root, F. M. (1915). Reproduction and reactions to food in the suctorian Podophrya 

 collini n.sp. Arch. Protistenk. 35, 164-196. 



Rudzinska, M. and Chambers, R. (1951). The activity of the contractile vacuole in 

 a suctorian {Tokophrya infusionum) . Biol. Bull. Woods Hole 100, 49-58. 



Rudzinska, M. and Porter, K. R. (1953). Submicroscopic morphology of structures 

 involved in the feeding of Tokophrya infusionum. Proc. Soc. Protozoal. 4, 9. 



Discussion 



Chairman: H. V. Brendsted 



M. M. Swann. I am interested in the idea of suction generated by expansion in view 

 of my own and Mitchison's work on membrane expansion as the possible mechanism 

 of cell division. In the light of our experiments on the modulus of cell membranes, I 

 think that 1 cm. of water is a possible figure. 



I should also like to suggest that a study of the flow up the tentacle with different 

 viscosities of protoplasm might help to settle whether suction is caused by expansion 

 or by peristalsis. A very low viscosity would help the first mechanism, but possibly 

 not the second. 



J. A. Kitching. The spherical shape of the organisms at the end of a good meal 

 supports the idea that they have been filled up, as though by peristalsis of the inner 

 tube of the tentacles. However, both mechanisms may operate. On the rather rare 

 occasions when wrinkling occurs during normal feeding, or when it is induced 

 experimentally by the use of a shrunk ciliate for food, the protoplasmic surface 

 certainly expands together with the pellicle; and the same is true in certain of the 

 pressure experiments in which the pressure used was not very high. In these cases 

 the expansion cannot be attributed to an internal pressure caused by peristalsis of 

 the tentacles. 



J. F. Danielli. Does the application of pressure stop the inflow of material from the 

 prey? 



J. A. Kitching. Pressures above about 4,000 lb. per sq. inch stop the uptake of food. 

 The tentacles attached to the prey, shortened during the feeding process, gradually 

 extend, and the prey is imperceptibly released. 



R. J. Goldacre. Can a comparison be drawn between the expansion of the surface of 

 Discophrya which occurs during feeding and the expansion of the surface of Amoeba 

 caused by fat-solvent anaesthetics? 



20J 



