Heredity m Protozoa 597 



bearing the spine in the thirteenth generation is therefore to be 

 designated ^i-i-i-i-^^^-i 



Fourteenth and fifteeiith generations. During the night of May 

 12 there were again two divisions, giving three normal individuals 

 and one with the spine. The spine is now situated at about the 

 middle of the body (Fig. 4, ^^). The only way this result can have 

 been reached is as follows: The spine went to the anterior indi- 

 vidual in both of these divisions, and in the growth processes after 

 each division it moved backward about one-fourth the length of the 

 body (or rather, the anterior tip grew forward that amount). The 

 individual of the fifteenth generation is therefore ^i2i-2i-2i-2.2.2.2.i.i.i_ 



The spine now bears a ball at its tip (Fig. 4, ^^). This is due to 

 the fact that at the time of fission some of the endosarc is squeezed 

 out through the tube of ectosarc, thus forming the ball. This 

 indicates that at the time of fission, or in the period of rapid 

 growth just following it, the internal contents must be under 

 much pressure. 



Sixteenth generation. The plane of fission (night of May 13) 

 passed just in front of the base of the spine, leaving the latter at 

 the anterior tip of the posterior individual (Fig. 4, "). Again 

 it failed to be displaced backward in the growth following fission. 

 The ball at the end of the appendage was gradually constricted off 

 from the tip, becoming completely separated at 10.15, May 14. 



Seventeenth and eighteenth generations. During the night of 

 May 14 the animal again divided twice. The method of division 

 is shown clearly by the fact that the three individuals without the 

 spine remained connected in a chain, only the animal bearing the 

 spine being free. The spine went to the anterior individual in 

 both fissions, being displaced backward about one-fourth the 

 body length in each growth period. 



Nineteenth generation. In the next division (night of May 15), 

 the spine went to the posterior individual, being borne again at the 

 anterior tip (Fig. 4, ^^). 



Twentieth and twenty-first generations. During the night of 

 May 16 there were two generations, the spine going to the anterior 

 individual in each case. This is demonstrated by the fact that the 

 three individuals without the spine have remained united in a chain 



