524 BULLETIN OF THE 



of the nucleus during the first phase of the intranuclear changes.* Al- 

 though the plane of division is seldom inclined sufiiciently to allow one 

 to look, even obliquely, on the pole of the prospective spindle, yet stel- 

 late arrangements of the scanty pigment granules and fat globules of 

 the protoplasm are to be seen. These Flemming compares, with justice, 

 to molecular asters. It follows from his observations, I think, that we 

 have as yet no grounds for presuming that the stellate figures in tissue 

 cells are dependent on preceding alterations of the nucleus, — certainly 

 not that they are brought about by a segregation or localization of nu- 

 clear substance. There is nothing in Flemming's figure of this stage 

 (Taf. XVI. Fig. 2 a), nor in the text, to indicate that there is at this time 

 any evidence of a dicentric arrangement on the part of the nuclear fila- 

 ments themselves. In cases where, from the absence of granules in the 

 protoplasm, these asters are not rendered visible, it is none the less prob- 

 able, as Flemming maintains, that they exist. 



But there are cases in which the division of the nucleus is in all prob- 

 ability not accompanied by such fundamental rearrangements of its 

 substance as appear in the various modifications of the spindle figure. 

 Thus far, I believe, no trace has been found of molecular asters in these 

 instances of direct nuclear division. That, however, does not warrant 

 the • conclusion that asters, being formed about a segregated portion of 

 the nucleus, are here wanting because no such localization of nuclear 

 substance has taken place. The only inference which seems to me justi- 

 fiable from this evidence is, that the filamentous and other differentia- 

 tions of the nucleus are correlated with the existence of molecular asters. 

 It aff'ords no means of ascertaining the nature of this relationship, and 

 therefore is without significance in any attempt to answer that question. 



As regards the evidence to be drawn from the so-called free nuclei, it 

 is too limited to be of great value. The view that these nuclei do not 

 arise de novo, but result from the division of previously existing nuclei, 

 has only recently been gaining support, and there are not many observa- 

 tions on their division. Whitman ('78", p. 272) has "seen these nuclei 

 (his entoplasts) pass through the successive forms of a dividing amphi- 

 aster," and Balfour ('78, p. 17) has shown that his "yolk nuclei" some- 

 times present much the same appearance of a double cone as do the 

 nuclei in the germinal disk. While the former observer certainly saw 

 the astral figures, the latter, it must be concluded, did not, for he gives 



* '*Wichtiger ist eine m?iere Veranderung im Zellenleibe : Schon in diesem Sta- 

 dium (1. Phase) existirt in ihm, wie ich kurz sagen will, eine dicentrische Anordnung, 

 den kiinftigen Theilungspolen der Kernfigur entsprechend." — Flemming, '78, p. 372. 



