Guilliermond - Atkinson — 128 — Cytoplasm 



coagulation of the cytoplasm which is in contact with the vacuoles. 

 Pekaeek thinks it is protein in nature. Weber thinks it does not 

 belong to the cytoplasm but to the vacuole and is the outcome of a 

 condensation about the vacuole of the lipides found in solution 

 within it. According to Eichberger, this perivacuolar layer is of 

 the same nature as the ectoplasmic layer, composed, like it, of pro- 

 teins and lipides but much more resistant. He examined the layer 

 over a period of several days in abiotic solutions, for instance in a 

 5% solution of copper sulphate and over a period of from two to 

 three hours in a 20% solution of calcium citrate, which proves that 

 it acts like an inert membrane and not like a membrane differen- 

 tiated and living, in the sense of DE VRIES. 



On the other hand, it is very difficult, if not impossible, to ob- 

 serve the vacuoles in embryonic cells and consequently to demon- 

 strate that they do not form de novo. Therefore the theory of 

 DE Vries and Went was contested by numerous botanists, among 

 others, Pfeffer and Nemec. Pfeffer, in particular, showed that 

 it is possible to produce artificial vacuoles in the Plasmodium of 

 Chondrioderma difforme by placing it in a solution saturated with 

 asparagin. The Plasmodium encircles the crystals of asparagin, 

 which, dissolving in the cytoplasm, form there vacuoles which are 

 indistinguishable in all ways from the pre-existing vacuoles. For 

 this reason, Pfeffer thinks that every particle found in the cyto- 

 plasm which will take up water more readily than it, is capable of 

 producing a vacuole. It is true that Pfeffer's experiment does not 

 demonstrate very much, for here it is a question of the production 

 of digestive vacuoles which are perhaps not the same as the other 

 vacuoles. 



The question of the origin of the vacuoles remained uncertain 

 for a very long time, because neither observation of living material 

 nor fixed and stained preparations made it possible, in general, to 

 follow the development of these elements. Vacuoles in living em- 

 bryonic cells can not ordinarily be distinguished and in fixed prep- 

 arations the vacuoles are always altered by swelling. 



Rapid progress in this field w^as not made until very recently 

 when investigators began to use vital stains. 



