246 c. iSHiKAWA : 



Protozoa ('94, c). The accumulation of nucleoplasm at the poles 

 of the spindle evidently corresponding to a part of the pole- 

 plate, as well as the mode of division of the archoplasm, also 

 stand in favour of the view I have taken. The archoplasm 

 lying outside the nucleus and containing a spherical body — a 

 centrosome — or a group of smaller bodies, produces after divi- 

 sion a large spindle, Avhicb, both in appearance and in the part 

 it plays iu nuclear division is like tlie " Central-Spindel " of 

 Heemann ('91), but difiers from it in that the fibres of the 

 spindle run directly between the two masses of archoplasm, and 

 not between the centrosomes, as they do in the "Central-Spindel," 

 as observed by Flemming ('87), Hermann ('91) and Heiden- 

 hain ('94, cl). For this reason I have called the spindle of 

 Noctiluca the *' archoplasmic spindle" ('94, c). 



Should we assume that the whole archoplasm represents the 

 centrosome, then not only the character of the central body or 

 bodies wdiich it contains, but also the formation of the radial 

 fibres out of the substance of the centrosphere instead of out 

 of the centrosome, becomes incomprehensible ; for here both the 

 central spindle-fibres and the radial fibres are formed out of the 

 archoplasm. On the other hand, the great similarity of this 

 extranuclear substance with the pole-plate of other Protozoa, is 

 shown by the fact that it does not send forth any astral rays 

 but only short pseudopodia-like processes, and such fibres as 

 go to attach themselves to the chromosomes. Especially remerk- 

 able is the resemblance between the fate of the spindle-fibres 

 and that of the micronucleus in Para7nœcium aurelia, as des- 

 cribed by K. Hektavig ("92, '95). I shall return to the discus- 

 sion of this subject under the heading of the elongation of the 

 spindle-fibres. 



