172 



REPRESENTATIVE SINGLE-CELLED ANIMALS 



transverse division (Fig. 93, 3 and 4), the pigment spot and reser- 

 voir also divide, and one member of each migrates to form the 



1. Free-swi moling Stage 



2. Longitudinal Fission in Active 

 Sta^e 



3. Transverse Fission in 



Active Stage 



4. Transverse Fission in Cyst 



5. Encystraent 

 without Fission 



6. Encystment with Longitudinal Fission 



7. Conjugation in free-swiraming stage 



Fig. 93. — Phases in the hfe cycle of Euglena gracilis. 

 (After Tannreuther.) 



pigment spot and reservoir of the posterior cell. While this is 

 taking place the nucleus divides, and a transverse constriction of 



