16.2 HOFMEISTER, ON 



mother-cells. Usually, however, immediately after the for- 

 mation of the secondary mother- cells, the tertiary mother- 

 cells, i. <?., the spore-mother-cells, are produced. 



Owing to the want of transparency of the cell-contents 

 the nucleus of the secondary mother-cells can with difficulty 

 be distinguished. It is, perhaps, impossible to make out 

 what part it plays in the formation of the spore-mother- 

 cells. A nucleus with a large nucleolus is very indis- 

 tinctly seen through the grumous contents of the perfect 

 tertiary mother-cell. The spore-mother-cells lie in twos, 

 very rarely in fours (PL XX, tig. 7), quite free and de- 

 tached in the inner cavity of the primary mother-cells. The 

 second condition can easily be looked upon as the result of 

 the suppression of the formation of the secondary mother- 

 cells. A long series of comparative measurements has con- 

 vinced me that the latter do not increase in size during or 

 after the formation of the spore-mother-cells, and if this be 

 so, the formation of the last-mentioned cells can only take 

 place by the occurrence of a considerable contraction of the 

 entire contents of the cell, either before or immediately 

 after its division into two halves, upon the entire surface 

 of which (two halves) cellulose is then secreted. I believe 

 that I have actually seen such a process of transition (PI. 

 XXI, fig. 9). 



The membrane of the mother-cells, primary, secondary, 

 and tertiary, is coloured pale blue by iodine. When 

 brought under water its substance swells rapidly, espe- 

 cially that of the inner younger layers. The membrane 

 of the tertiary mother-cells swells the most, that of the 

 primary ones the least. This peculiarity of the wall of the 

 spore-mother-cell affords one of the most striking proofs 

 of the independent nature of the primordial utricle. The 

 spore-mother-cell, when placed in water on the stage of 

 the microscope, rapidly swells to double its original size, 

 its wall being excessively distended. The cell contents, 

 which are plainly surrounded by a thin layer of soft matter 

 very like a delicate membrane, swell slightly or not at all ; 

 they (the cell-contents) lie free in the inner cavity of 

 the cell in the form of a closed vesicle, surrounded by 

 watery fluid. Individual points of the primordial utricle 



