president's address. 683 



interpreted in the manner proposed : appearances which, being 

 constant for the same cell under varying methods of treatment, 

 cannot be produced by the action of re-agents.* If such a cell is 

 watched while some fixing agent of a favourable character is 

 applied to it, the new features which come out appear, not like 

 something brought about by precipitation or streaming of vesicles, 

 in which case some trace of the movements would surely be 

 capable of detection, but very much in the same way as the 

 features of a landscape come gradually into view at dawn. No 

 part of the structure seems to be manufactured before our eyes ; 

 it merely gradually emerges into view. Thus we get regularly 

 arranged systems of lines which, if they ai-e not networks of fibrils, 

 are certainly very unlike division-walls between series of vesicles, 

 and arrangements of definite granules which are equally impossible 

 of interpretation in accordance with Biitschli's theory. We find, 

 moreover, in the cytoplasm certain bodies of a definite nature 

 which are observed to go through certain well-defined series of 

 changes, some of which entail movements of a restricted and 

 definite character. How are we to explain the phenomena of 

 karyokinesis in the absence of any fibrils or other guiding and 

 contracting elements within the cell 1 



This view of the matter has been forcibly put by Flemming : — 

 " Ich befinde mich in Einklang mit Kupflfer in der Meinung dass 

 wir in der That guten Grund haben hier wirkliche wenn auch 

 naturlich nicht starre sondern vital verandorliche Bauverhaltnisse 

 anzunehmen, nicht aber, wie andere meinen, eine emulsionartige 

 Masse, in der Stromungen und Kornchenaufreihungen kommen 

 und schwinden."f 



Moreover the definiteness of form observable in most unicellular 

 animals, and most cells of multicellular, seems to require some 

 other internal structure than mere vesicles. In the absence in 

 many cases of an external stifli" enclosing layer, how are we to 



* Apathy in a paper " Ueber die Schaumstruktur hauptsiichlich bei 

 Muskel- und Nervenfasern" (Biol. Centralbl. 11, 1891) denies that such 

 alveolar or frothy structure exists in nerve or muscle fibres. 



t " Ueber Zelltheilung," Verhandl. der deutsch. Anat. Gesellsch. 1891. 



