in the Aniiiud KiiKjdom. 3(5J 



does not had to tlie ^>//j/A/o/t-'^/taZ mulliiiUcation and repro- 

 duction of cellsj but, on ihe contrary, represents wliere it 

 occurs a degeneration or aberration, or perhaj).s in many cases 

 (torniation of nuiltinuclear cells by fragmentation) is subser- 

 vient to the metabolism of the cell by increasing the periphery 

 of the nucleus. According to this theory, therefore, if leuco- 

 cytes divide Avith fragmentation of tlieir nuclei, the products 

 of this process would no longer be material possessing repro- 

 ductive power, but, on the contrary, would be destined to 

 destruction, although they may still be able to continue to 

 live for a long time in the tissues and juices," 



Although Flemming writes the foregoing sentences merely 

 as probable hypotheses, and not as proved results, they are 

 nevertheless of great importance, and I'lemming's develop- 

 ment of his theme will largely contribute towards bringing 

 into general recognition the true interpretation of amitotic 

 nuclear division *. For many years past I have cherished a 

 similar view with regard to the biological import of amitotic 

 nuclear division to that which is expressed in the above- 

 quoted sentences of Flemming, and 1 have since found it 

 confirmed in all cases of amitotic nuclear division which have 

 come under my notice in literature ; I therefore believe that 

 amitotic nuclear division, wherever it appears, is to be inter- 

 preted in the sense of the exposition which I have just cited. 



The study of the nuclei in the periblast of Teleostei had 

 been my starting-point in such considerations f. " The 

 nuclei in the periblast of Teleostei divide at the time of seg- 

 mentation by karyokinesis, as a number of authors agree in 

 affirming j subsequently, however, they acquire a peculiar 

 appearance |, and exhibit the figures of direct nuclear 



* Amitotic nuclear di\i.sioii iucludes, according to Arnold's termin- 

 ology, " direct segmentation," *' direct fragmentation," and " indirect 

 fragaientation.'" 1 disregard Arnold's designations entirely, since, as it 

 appears to me, they are lased upon an unnatural classitication. 



T E. Ziegler, " Die Entstehuiig des Blutes bei Ivnochenfischem- 

 bryonen," x\rchiv f. mikr. Anatomic, ^(O 13d., Ib87, p. IGO. 



4. The same phenomena are seen not only in the case of the nuclei of 

 the other merobla^tic \'ertebrates which lie in the yolk, but also in that 

 of the yolk-contained nuclei of the Arthropods. Just as in the develop- 

 ment of the merublastic ova of Vertebrates it is in the highest degree 

 impiobable, and at least not yet proved, that the large nuclei lying in the 

 yolk take auy morphological share whatever in the building up of the 

 embryo, so the same assertion can be maintained for those nuclei which 

 in the Arthropods still remain in the yolk after the formation of the 

 blastoderm and of the rudiment of the primitive streak. I quote the 

 observations of Graber on this point (" Vergleichende Studieu iiber der 

 Embryologie der Insekten und insbesondere der Muscideu,'' iJenkschrifteu 

 der k. Akademie zu Wion, Math.-uaturw. Klasse, oG Bd., 1889) : — 



