THE STRUCTURE OF CELLS 



passively moved to their respective poles, and to possess no power of 

 automatic movement of their own. 



With the arrival of the chromosomes at their respective poles 

 the Anaphase stage supervenes. This consists practically in a 

 series of regressive changes which leads to the formation of normal 

 resting nuclei. The chromosomes lose their sharp outline and 

 swell up; at the same time the nucleoli once more reappear. The 

 chromatin, or as much of it as persists, is distributed through the 

 swollen linin just as it originally existed in the parent nucleus, and 

 finally a wall isolates the daughter nucleus from the surrounding 

 cytoplasm. But the cytoplasm still bears traces of recent dis- 



Fio 



Pelvetia canaliculuta, telophase ot 

 the second mitosis in the fertilised 

 (oospore). (Phil. Trans, of the 

 ' Society.) 



turbances, and the period of gradual restoration of quiescence in it 

 forms what is sometimes known as the Telopliase. 



The centrosome (when present) is often already doubled during 

 the meta- or ana-phase, but the astral radiations frequently do not 

 die away till much later. It is in the region of the interzonal 

 fibres that events of the greatest interest are now proceeding. In 

 animal tissues it very often happens that the two cells are constricted 

 equatorially, and they may ultimately become delimited from each 

 other, the remains of the interzonal fibres then remaining at this 

 spot, where they may be long recognised as the Intermediate Body. 

 In plants, owing to the existence of a cellulose skeleton, and the 

 close adherence of the cytoplasm to its internal surface, such a con- 

 striction does not usually arise. Instead of this the fibres increase 



