o76 Dr. II. E. Zieglev o/* Avo'tofic y^uclear Division 



tie giant cells *, wliicli arc met with in the .spleen, in the 

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

 one .side. 



From all tlie .^talemonts which have been brought forward 

 the reader will have ])erceived that in the Metazoa amitotic 

 nuclear division only occurs in those cases in whicli the nuclei 

 have adaj)ted themselves to a special function ; it always 

 points to the approaching dissolution of the nuclei. WaldeyerJ 

 is of the o))inion ihat the amitotic method of division is the 

 primary one, as being the sii.Mpler. The cases which occur 

 ni the Metazoa are totally unfitted to support this view ; 

 (iinifodc michar division in the Metdzoa ahcays npjiears as 

 necondari/y acquired. We have yet to discuss the occurrence 

 of amitotic nuclear division among the Protozoa. 



Since karyokinesis occur.s with such striking agreement in 

 the whole of the animal and the whole of the vecretable 

 kingdom, we may accordingly conclude that this process is 

 ])livlngenetically 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 Eugh/pha §, 

 and among the Heliozoa for Actinosplicerium \\ ; amoug the 

 Jiadiolaria, too, it ap])ears not to be al)sent, for Hrandt ^ has 

 ohsei ved iii the case of the small nuch'i of the 8pha3rozoids a 

 spindK'-sliaj)ed traiisformation during division. Among the 

 Flagellata Biitschli has seen in Euglena during the division 



* I caiiudt ventiue to enter into the liiscussiun of the obscure physio- 

 logical import of the jiiaut cells: I refer the reader to Fleinuiing's state- 

 ments (Archiv f. mikr. Aiiatouiie, Bd. 87, p. '2'd2). The oecinrence of 

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

 >if the bones itnd in turn* urs has recently been treated of in .Sinebes 

 paper, " Leber Kernteiliuip und liiesenzellenbildung in (tescliwiilsten 

 und ini Knochenmark," J)iss. vorg. d. med. Faiiultat zu Freiburg i. B.. 

 1890. 



t In many animals {e. g. the mcaise) tl>c occurrence of giant cells in 

 the spleen and in the marrow of the bones is so regular as to lead u-i to 

 regard it as the result of a normal rather tlum of a patliological process. 



I Waldeyer, " X'eber Karyokinese und ihre JVziehungen zu den 

 Befruchtungsvorgai gen,'" Art hiv f. niikro-k. .\untomie, 'i'l JM., 1S88, 

 p. 44. 



§ Schewiakdti", •' Leber die karvokinetisdie Keruteilung von FAiylytiha 

 dlveolatd," Morphul. Jahrbnch, lo Bd., lN'^7. 



II A. (Jruber. '• leber KeruteJlinigsvorgange l>ei eiuigeu Brotozoen," 

 Zeitschiift t. wiss. Zcologie, Bd. 8S, 18.S). -1\. llertwig, '" leber die Keru- 

 teilung bei ActihOfph<i-riuni JEic/iJioDii," Jeuaische Zeitschrift, J>d. 17, 

 JS4 1 



*t K. Brandt, "Die kolouiebildenden Radiolarien (Sphserozoen)." Faun.-^ 

 uiid 1 lora des Golfes von Xeai)el, \iii. Monojjr.iphie, Berlin. If^.). 



