Heredity in Protozoa 



607 



the previous generation. The spine itself was a httle longer (Fig. 



In the sixth generation it still further mcreased in length at 

 the time of division, and went again to the posterior individual 

 (Fig, 9, «). 



In the next two divisions the tooth went in each case to the pos- 

 terior product, and continued to grow smaller. It remained near 

 the posterior end, and in the tenth generation (^^772.2.1.2.2.1.2.2.2^ jj. 

 was hardly noticeable (Fig. 9, ^°). During the next division it 



Fig. 10 History of a race derived from an individual with a truncate anterior end. The numbers 

 indicate the generations figured. The truncate end is barely visible in generation 3, but had quite dis- 

 appeared in generation 4. 



disappeared completely, both products being typical individuals 



(Fig. 9, "). 



Thus this spine persisted through seven generations, first in- 

 creasing in size, then decreasing, till it disappeared. 



b Anterior End Truncate 



In three cases I followed the history of the progeny of individ- 

 uals having the anterior end short and sharply truncate, as if cut 

 off by a knife (Fig. lo). 



