304 BULLETIN OF THE 



is now composed of the two disks and a piece inter mediaire, the latter 

 being only slightly, or not at all, stained. During the constriction of 

 the body of the cell, which now takes place, and which does not en- 

 croach upon the band, there occurs in the piece intermediaire a differ- 

 entiation of substance at the niveau of the constriction. Treatment 

 with nitrate of silver causes the appearance of black points, which 

 become more and more numerous. These at length become aligned, 

 and form the partition separating the two produced cells. The parts 

 of the intermediate piece adjacent to the partition blend more and 

 more with the cortical zones of the produced cells; the part adjacent 

 to the polar disk becomes, on the contrary, granular, and gradually 

 blends with the medullary mass of the cell. The polar disk becomes, 

 as maintained by Strasburger, the nucleus of the produced cell, — not 

 the nucleolus, as claimed by Biitschli. It appears to enlarge at the ex- 

 pense of the small, clear mass to which it is joined, after the corpuscles 

 which form it are united into a homogeneous mass ; the latter takes an 

 oval form, and becomes more and more regular. The substance of the 

 young nuclei are stained less by carmine and hsematoxylin as the cell 

 enlarges. The body of the cell soon ceases altogether to be stained. 



A resume of this paper, togejiher with those of Auerbach ('74), 0. 

 Hertwig ('75), and Strasburger ('75), has been published in the Quar- 

 terly Journal of Microscopical Science, by Priestley ('76). 



Auerbach ('76) objects to considering the " Kernspindel " as equiv- 

 alent to the nucleus. It corresponds to the middle part of the karyo- 

 lytic figure,"* for the following reasons : — 



(1.) Its volume is usually greater than that of the nucleus. 



(2.) It does not have a sharp, but rather a very confused, limitation. 



(3.) It is to be found only at the time of, or after, the disappearance of 

 the old nucleus. It demands the use of chemical reagents to make a dif- 

 ferentiation within its substance apparent. This structural appearance is 

 the optical expression of regulated morphological conditions under which 

 the commingling, and subsequently the separation, of the two substances 

 proceed, — the expression of inequalities in their distribution, — and 

 indicates, on the other hand, those molecular displacements which are 

 incident upon the progressive elongation of the whole (figure). Toward 

 the end of the process there is formed in the equatorial plane, owing to 

 an elimination of the nuclear sap in the direction of the poles, a more 



* **Der bewusste liingsstreifige Korper ist nicht der Mutterkern, sondern der Mit- 

 teltheil der von mir sogenannten karyolytischen Figur, also ein Product der Ver- 

 mischung der eigentlichen Kernsubstanz rait dem umgebenden Protoplasnia. " 



