168 Dr. M. Verworn's Biological Studies of Protista. 



we cannot speak of a development. I cannot adopt this view, 

 for I certainly see in the chamber-formation of the Poljtha- 

 lamia a process which is no mere growth, for the chambers 

 are not equal and similar, and the Protistan has quite a diffe- 

 rent appearance when it has only a few chambers, and later 

 when it has many. This process seems to me much rather to 

 represent a true development, and I even believe that in 

 particular forms of shells this development will prove to be 

 available for the recognition of their phylogenetic relations. 



With regard to the relation between the faculty of regene- 

 ration and development, it would moreover be of interest to 

 examine in the case of very old individuals whether the 

 power of regeneration has also sunk to zero, as we must 

 assume to be the case. Further, it would be very desirable 

 to test such forms as Orbulina &c., which remain unilocular 

 throughout their lives, as to their regenerative faculty. At 

 any rate we should here meet with similar conditions to those 

 prevailing in the Monothalamous freshwater Rhizopoda. 



The demonstration of the influence which the nucleus 

 exerts in the regeneration of the shell in Polystomella seem a 

 to me to be of particular importance. Of late much attention 

 has been directed to the action of the cell-nucleus ; but, 

 although many naturalists have made observations upon its 

 functions, our knowledge of the matter still remains rather 

 limited. Besides the relations to reproduction which the cell- 

 nucleus displays, it has been endeavoured recently to investi- 

 gate its influence upon direct processes of change of material, 

 and the function of secretion especially has been claimed for 

 it. In the epithelial cells which secrete the chitinous rays of 

 the e^^ of Ne^a and Banutra^ Korschelt * observed that at 

 the period of secretion the nucleus acquires a peculiar lihizo- 

 podoid form, and emits pseudopodium-like processes towards 

 the side on which the chitinous secretion takes place. He 

 further convinced himself that all cells in which branched 

 nuclei are known to occur have a secretory character. As, 

 however, hitherto there was no direct observation of the share 

 taken by the nucleus in the secretory activity of the cell, it 

 is particularly interesting to become acquainted with such a 

 case in the regenerative processes of the Polythalamia. 



* Tageblatt cler 59. Versammluiig Deutsclier Naturforsclier unci Aerzte 

 in Berlin; No. 5. Sitzungsb. der Sekt. fur Zoologie. Korschelt, "Die 

 Bedeutung des Kerues fiir die thierische Zelle," in Sitzungsb. d. Ges. 

 naturf. Freunde zu Berlin, No. 7, lt*87. 



