Heredity di Protozoa 



619 



teenth generation I began to save all the progeny o^ a; up to this 

 time only the specimen bearing the spine had been kept alive. 

 In the large number of progeny thus obtained many variants were 

 to be observed in the matter of interconnection. Many individ- 

 uals were free and separate. Pairs of united individuals were very 

 common. Chains of three to eight or more (Fig. 20) were not 

 uncommon. These longer chains were likely to break apart in the 

 course of time, as a result of their bending and twisting move- 

 ments. 



Fig. 20 Chains of individuals formed in the history of the race a, as a result of incomplete fission. 



There was much variation in the extent and strength of the 

 union. Sometimes there resulted from the division of united indi- 

 viduals specimens that were quite free. The division of free 

 specimens often produced united pairs. In some cases the con- 

 necting band was very thick and strong, so as to hold the two 

 specimens inflexibly in various positions (Fig. 20, b). In other 

 cases the fission was so incomplete that mere partly double 

 specimens resulted (parts of d. Fig. 20). Finally, the irregularities 



