-2q5 Erste Sektion: Cytologie und Protozoenkunde. Erste Sitzung. 



heredity is a not improbable, though as yet unproven view. That 

 it functioned so primarily is however very unlikely. It is far 

 more probable that the chromatin arose primarily as a modi- 

 fication of primitive protoplasm, of metabolic, rather than hered- 

 itary function ; becoming later specialized for the latter, if indeed 

 such a function shall be finally proven to pertain to it. There 

 are man} 7 instances known to day, notably among Bacteria, of 

 cells which are either anucleate, or contain diffuse nuclear matter. 

 Now in these cases the nucleus, as a differentiated cell organ, does 

 not exist, and such was probably the primitive condition of 

 every cell. 



If it be granted then that the cell originally lacked a nucleus 

 how are we to suppose that the latter arose? A possible clue to 

 the answer is furnished by those cases in which new nuclei arise 

 from chromidia extruded from the nucleus. Here to be sure the 

 chromidia, and hence the new nuclei, come from preexistent 

 nuclei; but the gap between such a process and one in which the 

 chromidia arise independently, as has been claimed by Drze- 

 w e c k i (1904) in Monocystis, is perhaps not so wide as may be 

 thought. 



Admitting then the probability of the evolution of the nucleus 

 from undifferentiated protoplasm in primitive organisms, is it 

 altogether unlikely that among higher forms there may occur 

 some in which the specialized process of mitosis is undergoing 

 degeneration, and reverting to the primitive method of nuclear 

 development? Such a condition I believe I have found in cestodes, 

 in correspondence with their otherwise degener ate condition. 



The studies upon which this report is based cover a period 

 of six years and include the following species: Taenia serrata and 

 crassicollis, Thysanosoma actinioides , Moniezia planissima, Ano- 

 plocephala sp., Crossobothrium laciniaturn, Rhyncoboihrium bul- 

 bifer, Cysticercus sp., Coenums serialis, Tetrar hynchus crenacolle, 

 and larva sp. 



Both in larva and adult one finds masses of granulär proto- 

 plasm scattered among the meshes of the reticulum which com- 

 poses the framework of the Cestode body. Some of these masses 

 contain no evidence whatever of nuclei. In other masses may 

 occasionally be found darkly stained granules of varying size, 

 or delicate membranes within which no granules are contained. 

 These I interpret as the anlagen of nuclei arising de novo in cyto- 

 genic masses. The granules soon Surround themselves by mem- 

 branes, while within the empty membranes appear newly de- 

 veloped granules, and the new nuclei thus formed separate from 

 the cytogenic masses and take their place in the parenchyma 

 syncitium. 



Between different cells exist striking differences. Some show 



