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XLI. 



NOTE ON THE NUCLEI OF THE ENDOSPERM OF FRITIL- 

 LARIA IMPERIAL18. By H. H. DIXON, B.A. 



(Plate XXIV.) 



[COMMITNICATED BY DR. E. P. WEIGHT.] 



[Read NovEMBEK 11, 189~5.] 



The nmltinucleate protoplasmic lining of the embryo- sac of Fritillaria 

 imperialis has long been known as a very suitable object in which to 

 study the normal changes taking place in the nucleus during karyo- 

 kinesis. It is, however, not less remarkable for the variety of 

 extraordinary forms of nuclear division which present themselves 

 in it, especially before the formation of cell-walls in the protoplasm 

 surrounding the nuclei. As a rule, these nuclei are remarkable for 

 their size, and vary from -05 mm. to '025 mm. in diameter ; but 

 among these nuclei there are others which stand out conspicuously, 

 even in contrast with them, owing to their enormous dimensions. 

 Fig. 1, PI. xsiv., represents one of these giant nuclei, which measured 

 •3 mm. in length. The position in the sac of these nuclei does not 

 appear to be constant, though they seem to occur more frequently at 

 the distal end than at the proximal, and they are also usually found in 

 groups together. Their mode of division is generally direct, and the 

 phases they pass through during fission are often so peculiar as to 

 appear grotesque. Sometimes the whole enormous nucleus is seen to 

 break up into a number of small nuclei of very irregular shapes and 

 dimensions. These smaller nuclei remain connected together for some 

 time by narrow filaments formed by portions of the mother nucleus 

 which have become drawn out into thread-like forms.' Fig. 2 is drawn 

 from such a specimen. This figure also illustrates a peculiarity of 

 these direct divisions, namely, the occurrence between the severed 

 portions of the nucleus of regular striae in the protoplasm similar to 

 the spindle which persists for some time between two daughter nuclei 

 formed by karyokinesis. 



1 W. Flemming (Arctiv f. Mikrosk. Anatomie., 37, 1889) describes similar 

 connecting filaments bebveen the daughter nuclei formed by direct division in the 

 leucocytes of the Salamander. 



