290 BULLETIN OF THE 



siderable reduction in size through loss of nuclear fluid (Kernsaft) ; it 

 also loses its sharply defined membrane, although the existence of a 

 delicate one around the spindle the author finds probable from analogy 

 with the infusorian " semen-capsule." When the halves of the equatorial 

 zone have reached the ends of the spindle, the surrounding protoplasm 

 exhibits the radial structure already seen in other cases. Accompanying 

 a constriction of the protoplasm the nuclear spindle assumes a bandlike 



I 



appearance, with the dark granules of the zones occupying the ends of 

 the band near the centre of the nascent cells. The constriction of the 

 cell protoplasm is completed, and the two cells remain united only by 

 the band. The formation of the new nuclei now begins by the appear- 

 ance of a small, inconspicuous, clear space, filled with fluid, around the 

 dark granular mass of the ends of the band. The dark granules pass 

 into the interior of the new nuclei, and are the nucleoli. It is probable 

 that the fibres of the band divide in the middle, and that the halves are 

 absorbed into the corresponding nuclei. Very nearly identical results 

 were also obtained in the study of the embryonic red blood-corpuscles 

 of the common fowl. 



The following conclusions are, among others, drawn by Biitschli : that 

 the nucleus does not disappear in cell division, but only undergoes 

 a very remarkable reconstruction (Neubildung) ; * that the karyolitic 

 figure of Auerbach is most decidedly to be considered as the modified 

 nucleus. A complete dissolution of the nucleus is not to be thought of. 



It is evident from this paper that Biitschli now finds himself more at 

 variance with the conclusions of Auerbach than previously. Although 

 the author here refrains from expressing his opinion of the signification 

 of the radial figures, he remarks that to a certain extent he agrees with 

 Auerbach's views. Biitschli does not seem to have observed that these 

 radial figures arise before the complete formation of the spindle, and 

 does not mention, them as existing till the time when the lateral zones 

 reach the end of the spindle. His figures published by Strasburger 

 show, however, that he had observed these stars before the division ot 

 the median zone. 



* Lest "reconstruction" may appear an unwarrantable rendering of "Neubil- 

 dung," I take the liberty to quote the context, which will show the author's real 

 meaning. I must draw, says Biitschli, the following conclusions : ' ' Dass der Kern 

 bei der Theilung thatsachlich nicht schwindet, sondern nur eine hochst eigenthiim- 

 liche Neubildung erfahrt und dass die yielfach behauptete Neubildung der Kerne der 

 Tochterzellen nur insofern dem thatsachlichen entspricht, als dieselbe eine Umwand- 

 lung des in so eigenthiimlicher Weise modificirten Kernes in eine seiner urspriing- 

 hchen entsprechende Form ausdriicken soil. " (p. 430.) 



