494 J. A. DAWSON 



All the observations on cannibals have shown that the process 

 of digestion of the eaten animals is a normal one and proceeds 

 rapidly, although there is considerable variation in the time in 

 which equal numbers of swallowed animals are digested by dif- 

 ferent cannibals. A cannibal usually divides before the bodies 

 of swallowed animals are fully digested. In the second genera- 

 tion complete digestion takes place, as all animals in the third 

 generation which have been examined have been devoid of vis- 

 ible remnants of digestion, although they have a slightly greater 

 size. The result of this experiment shows that the complete 

 history of a cannibal from the first act of swallowing to the 

 almost complete resumption of normal size and appearance may 

 be carried out in time varying from ten to twenty-one hours. 



3. The effect of the culture medium 



Four typical animals were isolated on December 20, 1917, 

 from a mass culture coming from stock of culture A. When 

 each had divided twice, four subcultures, 1, 2, 3, and 4, were 

 begun and carried on depression slides, seven drops of medium 

 being used in each case. The animals of subculture 1 — com- 

 posed of four mass cultures, lA, IB, IC, and ID — were carried 

 in the culture medium and allowed to multiply, the medium not 

 being changed. 



The second subculture, composed of four mass cultures — 2A, 

 2B, 2C, and 2D — was carried in the same manner, but the 

 medium was drawn off frequently and fresh medium added. 



The animals in the third subculture, composed, of four lines — 

 3A, 3B, 3C, and 3D — were kept in the same medium and all the 

 daughter cells but one in each line were removed daily. 



The animals in the fourth subculture, composed of four lines — 

 4A, 4B, 4C, and 4D — were carried in the usual way, one animal 

 in each line being transferred to fresh culture daily. 



a. History of the sub-cultures, 1, 2, 3, and 4- A summary of 

 the history of the first two subcultures is given in tables 2 and 3. 



It should be noted that for the first four days there was no 

 essential difference in the division rate of the animals whether 



