142 Historical and Critical Considerations 



not seem very surprising. The phenomena of regenera- 

 tion of Vaucheria demand renewed investigation in this 

 respect also. As long therefore, as there is no actual 

 proof of a neogenesis of this organ, independently of the 

 old one, we cannot recognize such great significance in 

 this instance as some authorities attribute to it. 



Here also the observations by Haberlandt 26 on the 

 same phenomenon are important. This investigator di- 

 rected his attention chiefly to the nuclei, and familiarized 

 himself with their behavior during regeneration. The 

 nuclei accumulate near the wound in the plasma deprived 

 of chlorophyll bodies, and are evidently more important 

 than the latter for the growth of the new cell-membrane. 

 In the exuded globules of protoplasm which remained 

 alive, Haberlandt succeeded almost always in demon- 

 strating the presence of one or more nuclei, but never the 

 absence of any. In spite of this, not all of them formed 

 a new cell-wall. "At times there occur cell-forms devoid 

 of a membrane and rich in plasm. If the sap-cavity is 

 lacking, the chlorophyll-bodies aggregate in the center, 

 and the nuclei lie in the peripheral, colorless plasma. In 

 case a cavity for cell-sap is present, the chlorophyll-grains 

 lie in the innermost layer of the plasma-body the nuclei 

 more toward the outside." 27 The possession of nuclei is 

 therefore, in itself, not sufficient for the formation of a 

 cell-membrane. It would be important to find out whether 

 the parts of plasma referred to are perhaps the very ones 

 that did not get part of the old limiting membrane. 



It seems to me to be of great interest to regard the 

 whole pending question from another point of view, and 

 one which has already been considered by Haberlandt. 



26 Haberlandt, G. Ueber die Beziehungen zwischen Funktion und 

 Lage des Zellkernes. pp. 83-97. Jena, 1887. 

 27 Loc. cit. p. 92. 



