268 



I. 



THE CELL 

 I. 



I. 



Fig. 148. Conjugation of Paramecium (R. Hertwig, Zooh, Fig. 141): nl: paranuclei; fc 

 nuclei of conjugating animals. I The paranucleus transforms itself into a spindle ; in left- 

 hand animal the sickle-stage, in right-hand animal the spindle-stage, are represented. II 

 Second division of paranucleus into chief spindle (marked 1 in left, and 5 in right) and 

 subsidiary spindles (2, 3, 4 in left, and 6, 7, 8 in right). Ill Subsidiary spindles show de- 

 generation (2, 3, 4 in left, 6, 7, 8 in right), the chief spindles divide into male and female 

 spindles (1 into 1 m and lioin left, and 5 into 5 m and 5 w in right). IV Transmigration of 

 male spindles nearly completed (fertilisation). One end remains in the mother animal, 

 whilst the other has united itself with the female spindle of the other animal (1 m with 

 5 u-, and 5 m with 1 w). The main chief nucleus has become converted into segments. 

 V The primary division spindle resulting from the union of the male and female spindles 

 divides into secondary division spindles V and t". VI, VII After the termination of 

 conjugation. The secondary division spindles separate from one another, and come to lie 

 amongst the rudiments of the new paranucleus Ink'), and of the new chief nucleus (pt, 

 placenta?). The degenerated original nucleus commences to disintegrate. Since the Pam- 

 moBCium caudatum has been selected to demonstrate the initial stages, and P. aurelia 

 the final stages, I-III represent the former, and IV-VII the latter. The difference be- 

 tween the two consists in this, that P. caudatum has oidy one paranucleus, whilst P. 

 aurelia has two, and also that in the latter, nuclear disintegration commences even in the 

 first stage (stage I). 



