ZOOLOGY AND BOTA.NY, MICROSCOPY, ETC. 07 



work and form coarser meshes. (3) From the meshwork single 

 filaments arise, with irregularly coiled course. The filaments give off 

 small processes, so that their margins appear zigzagged. The granules 

 fuse to form Pfitzner's chromatin spheres, and the filaments finally 

 consist of alternate dark and clear discs. 



(4) The filaments become smooth, and are disposed parallel to one 

 another in the peripheral portion of the nucleus. Only a few processes 

 remain connecting the chromatin filaments in the so-called " close coil" 

 (dichte Knauel). (5) The filaments shorten and thicken to form the 

 " loose coil," and are at the same time bent into sickle shape. The 

 nucleolus now disappears. 



(6) The cytoplasm disposes itself radially to the surface of the 

 nucleus. The loops retire inwards, and have their apices directed 

 centrewards. The sun-form arises. (7) The cytoplasm of the clear 

 region begins to concentrate at the poles, the nucleus exhibits amceboid 

 'movements, the increase in size ceases, the nucleus becomes again 

 spherical. The accumulation of cytoplasm at the poles acquires a rayed 

 structure (the polar rays). The rays converge towards the poles of the 

 nucleus, and meet in a depression. Here arises the polar body, and at 

 the same time appear the spindle nuclear fibres. (8) The nucleus 

 becomes ellipsoid, the loops have their angles on the equatorial plane, 

 the stellate form begins. 



(9) The spindle-fibres grow from the poles into the nucleus, and 

 unite in the equatorial plane with those from the opposite side. A 

 continuous nuclear spindle is formed, which has a directive influence on 

 the chromatin loops. The nuclear spindle elongates in the direction of 

 the axis of division. The loops become disposed in two ways — the outer 

 remain parallel to the equatorial plane, the inner stand perpendicularly 

 to the same. The star-form is at its climax. 



(10) The loops become ribbon-like, and begin to divide longitu- 

 dinally. The inner loops are bent round to the polar end. The 

 longitudinal division occurs. (11) With re-arrangement the barrel 

 form arises, all the loops lie at right angles to the equatorial plane, 

 their apices are turned to the poles. (12) The loops separate, move 

 polewards, and arrange themselves radially round the somewhat flattened 

 polar body. Thus arise daughter-stars, and immediately after (13) the 

 daughter-sun-forms. (14) The nucleus is constricted into two, the 

 protoplasm of the clear zone is also divided, circulation begins in the 

 bodies of the daughter individuals, the plasma of the alveolar and 

 granular zones is divided between the two in approximately equal 

 portions. 



(15) Meanwhile the daughter nuclei undergo metamorphosis. The 

 polar body is drawn in, the loops are drawn out into filaments to form 

 the daughter-cells. (16) From the filaments connective threads proceed ; 

 a coarse and then a fine network is thus formed, the nucleolus reappears, 

 the nucleus acquires its normal structure. The plasmic circulation 

 ceases, pseudopodia issue from the opening of the cell, the daughter 

 individuals separate. 



Changes in nucleus and protoplasm appear contemporaneous. Only 

 the clear zone is active, the rest of the protoplasm passive. Whether 

 the penetration of the cyto-chylema into the nucleus is the very first 

 step or not the author does not venture to decide. The process is 

 clearly one of genuine division, and not, as Gruber maintained, half-way 



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