454 



WILSON. 



[Vol. XI. 



spindle-fibres are again resolved into the cytoplasmic net- 

 work. 



E. Later History of the Spindle and Asters. — In the fully 

 formed karyokinetic figure (Phototype 7, Text-fig. VI) the 

 spindle appears to be composed of rather stiff, well-defined 

 fibres having a somewhat irregular course, but so closely 

 crowded that it is difficult to determine whether they branch 

 or not. The rod-shaped chromosomes are arranged in a flat 

 plate extending entirely through the equatorial plane of the 

 spindle, and there is no indication whatever of a distinction 



VV..,vl 



•' ■: VMi'i .-" " ■!; \'. v.. A-, :-/"•■* 



'-J— ■:•■■: 'Z .'C\ I A }•<:'•/;•;; ■■'.■•■•l;:'-.'".' 'V-V" 



-•.-/■.i.',.v>-.-\< r-: 







Fig. VI. — The fully formed karyokinetic figure disappearing with a portion of the 

 surroupding reticulum, [cf. Phototype 7.] (42 minutes.) 



between a " central spindle " and a surrounding layer of 

 "mantle-fibres" such as Hermann has described in the case of 

 Amphibia. As the daughter-chromosomes move apart, the 

 space between them is occupied by conspicuous fibres (" inter- 

 zonal fibres") which differ from those of the distal portions' of 

 the spindle in no visible respect excepting that they are less 

 crowded. Soon, however, their course becomes more wavy, 

 they become granular, and by the time the daughter-chromo- 

 somes have reached the spindle poles their central portions 

 break up into separate blue granules, as a rule aggregated to 

 form a vague lenticular mass which appears to represent the 

 mid-body (" Zwischcnkorper ") of other forms (Phototypes 8, 9, 

 10, Text-figs. VIII, IX, X). As the cell divides, the remain- 



