128 PROTOPLASMIC ACTION AND NERVOUS ACTION 



the cell swells in hypotonic solution the thickness of the 

 hyaloplasm remains constant; apparently this thick- 

 ness is regulatively maintained by the transformation of 

 material derived from the internal protoplasm. Cham- 

 bers' observations on marine eggs show many interesting 

 instances of the formation of films at cut surfaces or at 

 the surfaces of protoplasmic fragments; regions where 

 the protoplasm is broken down by mechanical or other 

 injury soon become delimited by films bounding them 

 from the adjoining unaltered protoplasm.^ In the 

 formation of artificial vacuoles by the injection of 

 solutions into egg cells through micro-pipettes, films 

 with semi-permeable properties are formed about the 

 introduced droplets.^ The composition of the salt 

 solution is an important factor in the formation of such 

 vacuoles; Chambers has recently shown that pure solu- 

 tions of NaCl diffuse into the protoplasm without 

 forming films, while if sufficient CaCla is present, each 

 droplet of solution surrounds itself with a definite film 

 and forms a vacuole. A recent study by Seifriz^ of 

 the physical properties of protoplasm, as exhibited under 

 micro-dissection, gives many interesting details on film- 

 formation by living protoplasm under various con- 

 ditions. 



De Vries showed in 1885'' that the normal vacuoles 

 of plant cells are surrounded by membranes having the 

 same osmotic properties as the plasma membranes 

 (those inclosing the entire protoplast). In his experi- 



^ Chambers, loc. cit. 



2 Kite, loc. cit.; Chambers, Jour. Gen. Physiol. , V (1922), 189, 



3 Seifriz, loc. cit. 



^Jahrb. Tviss. Botanik, XVI (1885), 465. 



