140 Historical and Critical Considerations 



allows us to regard as possible an occasional neogenesis 

 of such organs out of pangens proceeding from the nu- 

 cleus. 



Judging from the facts published up to the present 

 time, however, the phenomena of regeneration after 

 wounding are closely connected with the normal pro- 

 cesses. Nobody, at least recently, has maintained that in 

 such a case there is a new formation of nucleus and chro- 

 matophores. There have been only few investigations in 

 regard to a possible occurrence of new vacuoles. These 

 were made by Went for the very purpose of testing the 

 point in question, and teach at least one thing with cer- 

 tainty, that so far, wherever it had been thought necessary 

 to assume a formation de novo of normal vacuoles, such 

 does not really take place. For the vacuoles which have 

 been observed originate partly through constriction from 

 the large sap- vesicle of the cell, and partly through the 

 swelling of the smaller ones which are suspended in the 

 granular plasm. Especially in the case of the Vaucheria, 

 which was studied first by Hanstein, and later by so many 

 investigators, there surely can no longer be a well founded 

 doubt on this point. 22 



Since the time when, in my "Plasmolytische Studicn" 

 I expressed the opinion and sought to establish the fact 

 that the plasmatic membrane is a separate organ of the 

 protoplast 23 no decisive facts on this subject have been 

 published. Klebs is opposed to my assumption on the 

 ground of an observation made on Vaucheria?* For the 

 study of these processes this investigator introduced a 

 new method, which makes it possible to demonstrate, 

 easily and with certainty, the beginnings of the formation 



22 Went, F. A. F. C. Jahrb. Wiss. Bot. 19: 330-341. 1888. 



jahrb. Wiss. Bot. 16: 493. 1885. 



** Arbeit en Bot. fust., Tubingen. 2: 510. 



