MUSEUM OF COMPARATIVE ZOOLOGY, 385 



words, " the active Kernstoff is uniformly distributed in the remaining 

 Kernsuhstanz,'^ as far at least as the optical evidence goes. While this 

 does not necessarily preclude the notion I have maintained, it certainly 

 gives a great appearance of accuracy to the view which recognizes in this 

 active (attractive) substance an essential part of the nucleus. Strasbur- 

 ger, however, is compelled still to recognize a separate active " Kernstoff," 

 without disclosing to us any of its properties save those which are mani- 

 fest by the radial phenomena. It therefore seems to me equally justifi- 

 able to apply to this active substance any other name than nuclear 

 substance. If one may call it nuclear substance because it is here sur- 

 rounded by or distributed through nuclear substance, then with equal 

 propriety it may be called in nuclear division a protoplasmic (vitelline) 

 substance. 



The importance of this substance which forms the centre of the aster 

 (" Kernsubstanz ") is thus formally announced by the author: " Meine 

 ganze Auffassung gipfelt in der zum Theil in dieser Auflage erst scharf 

 formulirten Behauptung, dass von der activen Suhstanz an den Keriipolen 

 die ganze Structur der Kerne und die Kerntheilung, die Structur des umge- 

 benden Zellplasma und dann die Zelltheilung hestimmt wird^ 



In a subsequent paper Strasburger ('77, p. 518) calls attention to a 

 case (Nothoscordum) in which the spindle fibres are exceptionally delicate, 

 and the nuclear plate is represented by rodlike elements arranged in 

 part around (outside) the equator. From this he concludes that the 

 elements of the nuclear plate are not simple swellings of the fibres, and 

 that in this particular case their repulsion from the poles was so forcible 

 as to result in their elimination from the spindle.* 



Treub ('79) has contributed interesting observations on the role of the 

 nucleus in the division of plant cells. His observations were made mostly 

 on the phanerogams, and especial attention was given to following the 

 steps of nuclear changes in living cells examined in a comparatively in- 

 different fluid. The time which intervenes between the different stages 

 figured is given. These observations are supplemented by studies of 

 alcoholic preparations stained in picrocarmine. 



The formation of the nuclear plate is accomplished (e. g. in the 

 "ovules" of Epipactis) without the intervention of a homogeneous con- 

 dition of the nucleus. The latter, at first finely granular and containing 

 a single nucleolus, at length contains a limited number of coarse, dis- 

 tinct, irregularly disposed granules. After the lapse of some time these 

 gradually accumulate at the middle (equator) of the nucleus to form di- 



* See also p. 350. 

 VOL. VI. — NO. 12. 25 



