NUCLEAK DIVISION OF NOCTILUCA. 253 



Whether the centrosome-like body in the spermatic cells of 

 plants exactly corresponds with the centrosome or the attraction- 

 sphere of animal cells or not, its behaviour in the formation of 

 cilia makes it very probable that it represents at least an ana- 

 logous organ. At all events, it is of great interest to observe 

 that similar processes are met with in the formation of the 

 motile organ i. e., (cilia or iingella) of the cells in Flagellata, 

 Algœ, Gymnosperms and Vertébrales, wherein the centrosome 

 or the centrosome-like body plays the most important part. 

 Furthermore, the direct conversion of the central or archo- 

 plasmic spindle-fibres into the flagellum of spores in Noctiluca, 

 is probably to be looked upon as an interesting contribution to 

 the knowledge of the archoplasm. 



But it is only the fibres of the archoplasm that are trans- 

 formed into the flagellum. The greater part of it is seen in 

 ripe spores as a darker area occupying nearly the entire ante- 

 rior part of the body in front of the nucleus (Fig. 11). 



-!>. The Elongation of the Fibres of the 

 Archoplasmic Spindle. 



Drüner ('94, e) in his investigation on the mechanism of 

 cell-division has given an ingenious explanation of the separation 

 of the poles of the spindle by elongation or active growth of its 

 fibres. This can be very beautifully demonstrated in the divi- 

 sion of the nucleus of Noctiluca, as was done by R. Hertwig 

 ('92) in the case of the micronucleus of Paramoecium, in which 

 the kinetic centres of division lie within the nucleus. 



In Figures 7, 8, and 10, Pt. XIX, are seen three spore- 

 forming cells in division, in which the central spindle is bent 



