.376 Dr. H. E. Ziegler on Amitotic Nuclear Division 



tie giant cells "^j wliicli are met with in the spleen, in the 

 marrow of the bones t, and in tumours, I leave entirely on 

 one side. 



From all the statements which have been brought forward 

 the reader will have perceived that in the Metazoa amitotic 

 nuclear division only occurs in those cases in which the nuclei 

 have adapted themselves to a special function ; it always 

 points to the approaching dissolution of the nuclei. Waldeyer:|: 

 is of the opinion that the amitotic method of division is the 

 primary one, as being the sin)pler. Tiie cases which occur 

 m the Metazoa are totally unfitted to support this view ; 

 amitotic nuclear division in the Metazoa always appears as 

 secondarily acquired. We have yet to discuss the occurrence 

 of amitotic nuclear division among the Protozoa. 



Since karyokinesis occurs with such striking agreement in 

 the whole of the animal and the whole of the vegetable 

 kingdom, we may accordingly cojiclude that this process is 

 phylogenetically a very old one, and was already generally 

 distributed in the common ancestors of animals and plants. 

 ]n agreement with this is the fact that mitotic division is 

 observed in almost all classes of the Protozoa. Among the 

 Ehizopods it has been clearly established for EugJypha §, 

 and among the Heliozoa for Actinosplicerium \\ ; among the 

 Kadiolaria, too, it appears not to be absent, for Brandt ^ has 

 observed in the case of the small nuclei of the Sph^rozoids a 

 spindle-shaped transformation during division. Among the 

 Flagellata Biitschli has seen in Euglena during the division 



* I cannot venture to enter into the discussion of tlie obscure physio- 

 logical import of the giant cells ; I refer the reader to Flemming's state- 

 ments (Archiv f. mikr. Anatoniie, Bd. 87, p. 292). The occurrence of 

 direct nuclear division and of the formation of giant cells in the marrow 

 .if the bones and in tumours has recently been treated of in Str.iebe's 

 paper, " Uebi-r Kernteihuig and Rieseiizelleubildung in Geschwiilsten 

 und im Knochenniark," Diss. vorg. d. med. Fakultjit zu Freiburg i. B., 

 ] 890. 



t In many animals (e. rj. the mouse) the occurrence of giant cells in 

 ih.e sph^en and iu the marrow of the bones is so regular as to lead us to 

 regard it as the result of a normal rather than of a pathological process. 



X Waldeyer, " Ueber Karyokiuese uud ihre iJeziehungen zu den 

 liefruchtungsvorgai gen," Arcliiv f. mikrosk. Anatomic, 32 Bd., 1888, 

 p. 44. 



§ Schewiakiitf, " L'eber die karyokinetische Kernteilung von Emjlypha 

 alveotaia,' Morphol. Jidirbuch, 13 Bd., 1887. 



II A. Gruber, " Leber Keruteilungsvorgiinge l)ei einigen Protozoen," 

 Zeitschiift f. wiss.Z('0^ogi.>, Bd. 38, 1883.-R. Ilertwig,'' Ueber die Kern- 

 teilung bei Actino)<p}ucriiim Eiclihorni^^ .Tenaische Zeitsclirift, Jid. 17, 

 1844. 



11 K. Brandt, " Die koloniebildenden Radiolarien (Sphaerozoen)," Fauna 

 uud I'lnra des Golfes ^ on Neapel, xiii. Monographie, Berlin, 1885. 



