232 PROTOPLASM 



recently produced vacuoles artificically in the protoplasm of 

 Myxomycetes by introducing small crystals of asparagin and 

 other soluble matters into it, so that counter evidence seems to 

 be presented from this side also. 



What de Vries brings forward with regard to the independent 

 wall belonging to the vacuoles seems to me in any case little 

 suited to prove its existence. In the normal vacuole he has seen 

 nothing more than the limiting margin, which is easily explained 

 on our view ; on the other hand, he and Went have observed 

 often enough how vacuoles flow together and become rounded 

 off again after their fusion. This, however, presupposes absolute 

 fluidity in the membrane, if for once we admit its existence. 

 And how does it harmonise with this view when de Vries 

 (1886, Dros., p. 33) says, " This wall must, like living protoplasm, 

 be exceedingly extensible and elastic, and impermeable to 

 colouring matters " ? Membranes extensible and elastic, but at 

 the same time fluid, are not very conceivable. Pfeffer (1886) 

 has therefore remarked very correctly, that the assumption of 

 de Vries that the wall of the large central vacuole of the 

 plasma cells was stretched elastically to a high degree, is very 

 improbable, since nothing can be seen of it in cutting through 

 the cell. Now de Vries has chiefly tried to prove his view of a 

 peculiar membrane belonging to the vacuole by plasmolytic 

 experiments on Spirogyra. Under the influence of a solution 

 of 1 per cent KN0 3 + Eosin which was used for these experi- 

 ments the vacuole with its wall was said to contract strongly, 

 and to remain living for a long time, while the protoplasm 

 quickly dies. The latter conclusion is drawn from the protoplasm 

 soon becoming stained with eosin, while the colouring matter 

 does not diffuse into the contents of the vacuoles, thus proving 

 the living condition of the wall. Now I have already remarked 

 above that the figures of de Vries are very coarse and 

 diagrammatic, and give no sort of information as to finer rela- 

 tions, on which account I consider it an admissible supposition 

 that the author has not carefully occupied himself with 

 finer microscopical details. It also seems to me not impossible 

 that the interpretation of the microscopic image given by de 

 Vries both here and in Drosera (1886) is incorrect. De Vries 

 gives us in fact no clue as to what is in reality present between 

 the wall of the strongly contracted vacuole and the frequently 

 only very slightly contracted thin utricle of protoplasm. I 

 should suppose that between the two lies a very strongly 

 vacuolated protoplasm. I imagine in my own mind that through 

 the action of the KNO S solution water is drawn out of the vacuole, 

 and it therefore becomes considerably diminished in size, but at 



