558 



is difficult, to say the least, to conceive how any equal division of 

 nuclear elements such as Weismann's theory demands could occur in 

 the budding of a minute nucleolus from a larger one. Moreover, it 

 is probable that at least in many cases the new nucleolus arises in- 

 dependently of the old. That a chromosome is temporarily an indi- 

 vidual may be readily admitted; that it may persist through several 

 cell-generations is possible, but my observations indicate that in Mo- 

 niezia, at least, it is not of fundamental significance, being merely the 

 product of temporary conditions and persisting as long as these persist. 



In conclusion attention may be called to one other point. The 

 cells which give rise to the sexual cells in Moniezia do not differ visibly 

 in any way from the cells of the parenchyma. Apparently those nuclei 

 which are affected by certain conditions develop into sexual cells while 

 those not thus affected may develop in other directions. Yet the 

 parenchymal syncytium with its branched protoplasmic outgrowths and 

 fibres shows a considerable degree of cytoplasmic differentiation , in 

 other words its cells are essentially tissue- cells, not a reserve stock 

 taking no part in the formation of the body. Nevertheless, some of 

 them become "germ-cells". While I am aware that visible differentiation 

 or the lack of it is not necessarily a criterion of actual differentiation 

 or its absence, yet I beUeve that these facts possess a certain signi- 

 ficance as indicating that there is no fundamental and continuous 

 distinction between tissue-cell and germ-cell. The cells become what 

 conditions determine. In my opinion the cell, so far as it is an indi- 

 vidual at all, is primarily a physiological and not a morphological in- 

 dividual. The attempt to force morphological interpretations upon 

 cytological phenomena can only lead us far from the real facts. 

 Hull Zoological Laboratory, university of Chicago, August 1904. 



(Eingegangen am 12. September 1904.) 



Nachdruck verboten. 



lieber die Nervenendigungen in den GrRANDRYschen und 

 HERBSTsclien Körperchen im Zusammenhange mit der Frage 



der Neuroneutheorie. 



Von Prof. Dr. A. S. Dogiel in St. Petersburg. 



Mit 10 Abbildungen. 



In der vorliegenden kurzen Mitteilung beabsichtige ich nicht näher 



auf die Literaturangaben über die Nervenendigungen in den Gran- 



DRYscheu und HERBSTschen Körperchen einzugehen, ich verweise nur 



