Diversity Produced by Conjugation 159 



In the descendants of those that have conjugated the 

 number of fissions in 21 days varies from 8 to 30, as 

 compared with 21 to 26 in the others. There are now 

 strongly marked differences between the different families 

 that have descended from those that have conjugated. It is 

 interesting to compare the records of fissions by two-day 

 periods for a considerable time in such families derived 

 from different ex-con jugants. Typical examples are as 

 follows : 



Family 



All these families were kept under the same conditions, 

 yet they consistently differ in their fission rates throughout 

 the entire period. They have become hereditarily diverse 

 in this respect, as a result of conjugation, for all were 

 derived, before conjugation, from the same original par- 

 ent, and all had the same rates of fission. Conjugation 

 has produced from a single stock a number of hereditarily 

 diverse stocks. The same thing was demonstrated in a 

 number of extensive experiments. 



Another respect in which conjugation increases the 

 hereditary differentiation is in the matter of abnormalities. 

 If we begin with a set of the animals that are all quite 

 normal, showing no inherited abnormalities, and allow them 

 to conjugate, we often find that many of the families pro- 

 duced have hereditary abnormalities, while others have none. 

 Such hereditary abnormalities, produced as a result of con- 

 jugation, are shown in Figure 44. In work by Dr. Stock- 

 ing (1915), of 450 families descended from animals that 

 have conjugated, 262, or more than half, showed hereditary 



