CONJUGATION IN VORTICELLA 211 



of division may again divide, giving rise to four microgametes, 

 but a single binary division is the rule.* 



The microgametes when set free from the parent stalk swim 

 through the water. Conjugation begins towards the hour of 



Fig. 45- 



Stages in the conjugation of Vorticella monilata ; mac, macrogamete ; 7nic, micro- 

 gamete. My fragmented macronucleus of the macrogamete. M ', fragmented 

 macronucleiis of the microgamete. W, water accumulated below the peristome 

 of the macrogamete ; yn, raicronucleus of the macrogamete ; ni', micronucleus of the 

 microgamete ; en, combination nucleus. For further description see text. (After 

 Maupas.) 



daybreak and lasts from thirteen to fourteen hours. A micro- 

 gamete coming into contact with a fixed macrogamete attaches 

 itself by its posterior end to the hinder region of the body of 

 the latter, and immediately becomes intimately fused with it. 



* It is so commonly stated that Vorticella gives rise by three successive 

 binary divisions to eight microgametes that it is well to insist on the fact 

 that Maupas has found that the microgametes are formed by equal binary 

 division in V. nionilata, V. putrina, and V. nebidifera ; by unequal binary 

 division in V. microstoma ; and only by repeated binary division in the case 

 of Carchesiiim folypinum. 



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