CHAP. IV 



OPAIJXA 



281 



have studied are mostly uninucleate as well as uni- 

 cellular (compare, however, Fig. 67, B, and pp. 265 and 

 269) : the higher animals consist of numerous cells each 

 with a nucleus : Opalina, on the other hand, is multi- 



~n it 



Flu. 73. Opalina ranarum. 



A, living specimen, surface view, showing longitudinal rows of cilia. ( x 35.) 



B, the same, stained, showing numerous nuclei (nu) in various stages of division. 

 (^ 50.) 



C, 1-6, stages in the division of a nucleus. 



D, longitudinal fission. 



E, transverse fission. 



F, the same in a specimen reduced in size by repeated division. 



G, final product of successive divisions. 

 H, encysted form. 



I, uninucleate form produced from cyst. 



K, the same after multiplication of the nucleus has begun. (From Parker's 

 Biology : A C, after Pfitzner ; D K, from Savile-Kent, after Zeller.) 



nucleate but its protoplasm is undivided, so that it 

 presents a condition of things intermediate between the 

 unicellular and the multicellular types of structure (see 



