Guilliermond - Atkinson — 16 — Cytoplasm 



TON, however, to the supposition that the ectoplasmic membrane 

 differed in its chemical constitution from the rest of the cytoplasm 

 and that it was composed essentially of lipides. Other physiologists, 

 for similar reasons, have considered this membrane as a sort of 

 mosaic, formed of lipide and protein particles (Nathansohn, 

 Clowes). The objection raised was that there were no morpho- 

 logical facts to confirm this hypothesis, and that the work of 

 Mayer and Schaeffer, as well as that of Faure-Fremiet, demon- 

 strated that the cytoplasm is a lipo-protein complex and that the 

 lipides are therefore scattered throughout all the cytoplasmic sub- 

 stance. There are, however, strong reasons for thinking that the 

 ectoplasmic layer does not have the same chemical constitution as 

 the rest of the cytoplasm but that it differs in being very much 

 richer in lipides. Indeed, in a complex liquid the lipides (lecithin, 

 phytosterol, etc.) which act more strongly on surface tension than 

 proteins, must, according to GiBBS' law, accumulate more at the 

 surface. This constitutes an argument in favor of the existence of 

 an ectoplasmic layer richer in lipides than the rest of the cytoplasm 

 (NiRENSTEiN, Hanstein, Czapek). The work of Rayleigh, De- 

 VAUX, and Langmuir have shown that oil put into water comes to 

 the surface where it forms a thin layer, and that its molecules have 

 an orientation which brings about an electrical polarization, per- 

 haps comparable to that which is encountered in the ectoplasmic 

 layer. 



Physiological properties of cytoplasm:- Protoplasm is irritable. 

 According to Sachs' definition, irritability is the capacity of living 

 organisms to react in certain ways under the most diverse influ- 

 ences of the external world. This very complex characteristic is 

 qualified as physiological or biological because until now its physico- 

 chemical mechanism has not been known. It is manifested by 

 specific reactions dependent upon the differences between cells. 

 This characteristic is common to all the morphological constituents 

 of the cell (nucleus, chondriosomes), but is especially easy to ob- 

 serve in the cytoplasm itself. One of the most wide-spread re- 

 actions of cytoplasm and the easiest to perceive is motility or 

 contractibility, i.e., the property by which the cytoplasm changes 

 from place to place. 



This quality can be observed in the Myxamoebae and the Plasmo- 

 dia of the Myxomycetes where the cells lack walls. Here motility is 

 manifested by changes of form and by displacements. Other cells 

 possess permanent extensions of the cytoplasm in the shape of fla- 

 gella or vibratory cilia which execute movements of rotation and 

 oscillation and act as locomotor organs (zoospores and anthero- 

 zoids). Besides these external movements, the cytoplasm usually 

 shows internal movements, as discovered in 1774 by CORTI and later 

 observed by Treviranus. These movements are called rotation, cyc- 

 losis or circulation of the cytoplasm, and have been already men- 

 tioned in these pages. They are found in most plant cells having 

 walls, where they are the only manifestations of cytoplasmic motil- 



