438 XXXII. CELL-DIVISION AND NUCLEAB DIVISION. 



granular, and, with stronger magnification, we note that they 

 elongate into a thin thread, bent zigzag to and fro (Fig. 9, and 

 the upper cell of 1). The coils of this thread .become longer, 

 produce loops constantly increasing in number ; these ultimately 

 anastomose, and so form gradually (10 and 11) the stage which 

 formed the starting-point of our observations. At the same time 

 the two daughter nuclei increase in size, and we assume -that 

 they are nourished at the expense of the surrounding cytoplasm. 

 They approach slowly nearer to the newly-formed partition wall. 

 About an hour and a half after the commencement of the separa- 

 tion the formation of the daughter nuclei is complete, and even 

 nucleoli are visible in them (11). 



The stages of division (karyokinesis) in the hairs of Trades- 

 cantia do not in general fix very well. The best results can be 

 obtained with chromosmium acetic acid (chromic acid 0-5 per 

 cent., osmic acid 0-2 per cent., glacial acetic acid 0-2 per cent.), 

 the so-called " Flemming's Fluid ". The objects thus fixed are com- 

 pletely freed from acid by prolonged soaking in water, and then 

 stained slowly, in part with very dilute watery safranin solution, in 

 part with fuchsin iodine green. We can thus determine (cf. Fig 153) 

 that the barrel-shaped mass of plasma, lying between the two 

 daughter nuclei, in which the partition wall is formed, and which 

 in the fresh state appears clear as glass, really consists of threads 

 which connect together the two rudimentary daughter nuclei. 

 We designate these threads as connecting threads (spindle- 

 fibres) ; the most median have a straight course ; the rest describe 

 curves so much the more arched in proportion as they approach 

 the edge of the system. The dot-like bodies which form the cell- 

 plate are now still more clearly visible, and appear with stronger 

 magnification as equatorial swellings of the individual connecting- 

 threads. 



Nuclear Division in the Pollen Mother-cells of Liliacecz. In 

 order quickly to obtain the stages of division of nuclei and cells 

 in a fixed condition, we turn to the pollen mother-cells of the 

 Monocotyledons. Especially to be recommended are many Lili- 

 aceae (Fritillaria, L ilium), and Amaryllidaceae (AlstroRmeria), 

 which possess especially large pollen mother-cells and nuclei. 

 These genera are relatively so like that they can mutually replace 

 one another. It is, however, of great advantage to select plants 

 that have in their inflorescences numerous flowers which open 

 successively, since we can find by experiment only which bud is at 



