416 DR. E. KLEIN, 



generally belong to the deepest layer^ but they soon become 

 shifted into the next following stratum. 



A point of great importance is the relation of the fibrils of 

 the nucleus in the different stages of division to the cell sub- 

 stance itself. I have on two occasions (this Journal, July, 

 1878, and April, 1879) referred to a connection of the fibrils 

 of the intranuclear network with the reticulum representing 

 the protoplasm of the cell, and on carefully examining my 

 specimens of dividing nuclei I find that also the fibrils of 

 these are intimately connected with the cell substance. The 

 forms mentioned as rosette or wreath, but especially as 

 monaster, are those in which — the examination being greatly 

 facilitated by the absence of any membrane — in many 

 instances I can most positively see a direct connection 

 between the fibrils of tlie nucleus and the reticulum repre- 

 senting the cell substance. Such a connection will be 

 found represented in figs. 14 — 19 of Plate XVIII. It is 

 true the observation requires very favorable conditions, viz. 

 the nucleus must be a large one, must be seen on its broad 

 surface, the light must be good, the sections thin, and the 

 power high. Zeiss's new oil immersion, -^ and -j-L-I inch, 

 have proved here invaluable. 



The fibrils of the nucleus taking the staining very deeply 

 seem at first altogether distinct from the surrounding cell 

 substance, which is either not at all or only slightly stained, 

 but nevertheless, on careful inspection, it will be found that 

 the fibrils, especially of the monaster, although they appear to 

 terminate singly in the periphery and with a blunt extremity, 

 do not so terminate but pass on, unstained, into the reticulum 

 of the cell substance. The difference of the fibrils of the 

 nucleus and the cell substance in their staining power is no 

 doubt due to an essential chemical distinction, but this does 

 not necessarily imply that the two substances cannot form an 

 anatomical continuity. Nor, it seems to me, does the 

 observation by Schleicher (' Archiv f. mikr. Anat.,' Bd. xvi., 

 p. 261) of the peculiar state of contractility — '' karyokinesis " 

 — of the nucleus of cartilage cells preceding division, nor that 

 by Peremeschko of similar appearances in the dividing 

 nucleus of epithelial cells of embryo Triton, make such a con- 

 nection between cell substance and nucleus improbable. 



By the observations of Strieker (' Sitzungsber. d. k. Akad. 

 d. Wiss.,' Vienna, June, 1877) it is established that the 

 nucleus of some colourless blood-corpuscles possesses con- 

 tractility while within the cell as well as after separation 



1 Tliese two leases, although of very great magnifying power, are never- 

 tiicless marvellous iu sharp definition. 



