1.84 



DIRECT AND INDIRECT DIVISION OF NUCLEI. 



"With the discovery of the wide-spread occurrence of karyokinesis there was for 

 a time a tendency manifested to deny altogether the possibility of the more direct and 

 simple process of nuclear fission. It is now usually held that this simpler process may 

 occur, although it is not easy to adduce entirely satisfactory evidence of amitotic 

 instances of nuclear division. No doubt elongated nuclei are frequently to be seen with 

 two nucleoli and with a constriction, more or less pronounced, in the middle, partially 

 dividing them into two parts, but hitherto no competent observer has seen and 

 described all the stages of simple fission proceeding in one and the same nucleus in 



Fig. '211. EPITHELIUM-CELLS OF SALAMANDER-LARVA IN DIFFERENT STAGES OF KARYOKINESIS. THE 



CELLS WERE HARDENED IN PICRIC OR CHROMIC ACID, AND STAINED WITH H.EMATOXYLIN OR SAFRANIN. 



HIGHLY MAGNIFIED. (Flemming. ) 



a, resting cell, showing the nuclear network ; b, first stage of division, the chromoplasm transformed 

 into a skein of closely contorted filaments ; c, second stage, filaments larger and less closely arranged : 

 in this and all the other figures except a the nuclear matrix is clear ; d (rather more magnified than the 

 rest), filaments larger and showing an arrangement in loops : this is more evident in e, where they 

 collectively have a rosette-like appearance enclosing a central clear space ; /, filaments converging 

 towards the centre ; g, stellate phase or aster ; A, completion of longitudinal splitting of the filaments 

 which is already beginning in / and g ; i, commencing separation of filaments into two groups (meta- 

 kinesis) ; j, further separation into two sets ; k, separation more advanced ; I, stellate phase of 

 daughter-nuclei (dyaster) ; m, commencing convolution of the filaments ; n, filaments more contorted ; 

 o, p, gradual passage of daughter-nuclei into condition of rest (network, q). The division of the proto- 

 plasm is seen to begin in the stage represented by in and to be rapidly completed (at n), 



the manner in which the process was believed to occur prior to the discovery of 

 the mitotic process. Lymph-cells were for a time often instanced as exhibiting the 

 amitotic changes, but, as it would appear from Flemming's researches, on entirely 



