820 



C. ISHIKAWA. 



inanv vegetable cells the cytoplasmic oriiiin of the spindle fibres. 

 In Spirogyra poJytojniata a part of the cytoiJasm— the kino- 

 plasm — differentiates itself in the form of parallel fibres on l^oth 

 sides of the flattened nucleus, even when the nuclear wall is very plainly 

 to be seen. Meanwliile the nucleus becomes flatter than before, and 

 the chromosomes ari-ange themselves in the equatorial plane. The 

 parallel fibres come now to lie seen distinctly within the nucleus on 

 both sides of tlie equatorial row of chromosomes. The fibres are. 

 according to Slnishunjer, the same fibres as were seen outside the; 

 nucleus and have pnshed into the nucleus through the sieve-like pores 

 formed in the nuclear wall, and attached themselves to the chromo- 

 scmies. The nuclear membrane disappears after this, and a perfect 

 spindle with the ecjuatorial row of chromosomes is formed (34^ p. 

 11). In the nuclear division of the ])rot()])lasmi(' l]'^tind}>eh'(i of the 

 embryo-sac of Leucojum a^stivum, the same author describes the 

 formation <^f the spindle out of the cytoplasm surrounding the nucleus 

 at the time when the miclear wall still exists. In the ])ollen- 

 mother-cells of Lilium biill)iferum (3Q. |>. 1 8::}-183). ^Ym.s7rH/y/^/' 

 describes the formation of the sjundle as like that in Spirogyra. 

 Here twelve fibres are thrown out from both the Ct'tttrosjilnnrs towards 

 the centre of the nucleus and push into its interior, and then, 

 the nuclear wall bec<)niing indistinct, ;i perfect spindle is formed 

 by the union of the free ends of the fibres at the ec[uator. In 

 his latest paper (36) StraiyJmrgcr still holds liis views as to the cyto- 

 plasmic origin of the spindle-fibres for plant cells. On the other hand, 

 Fßtzwr (28, I». 6o5). Iluhl (30, p. 26\)), Z<irhnrias (39, p. 852 ; 40, 

 p. o34), (L llniiriii ( 22, p. 16o). and others, believe in the tin-mation 

 of the spindle fibi-es out of the nuclear substarice. <>. Hcrtwiij «m this 

 point says (22, ]>. Ki.H):- — " l>ei einzelnen ^lollusken (Ptei-otrachea. 

 Phyllirhoë) liaben Fol und ich beobachtet, das« die Polspindel im 



