CHAP. IV 



OPALINA 



281 



studied are uninucleate as well as unicellular (compare, 

 however, Fig. 67, B) : the higher animals consist of numerous 

 cells each with a nucleus : Opalina, on the other hand, is 



FIG. 73. Opalina ranarum. 



A, living specimen, surface view, showing longitudinal rows of cilia. 



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



C, i6, 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 Saville Kent, after Zeller.) 



multinucleate but its protoplasm is undivided, so that it 

 presents a condition of things intermediate between the uni- 

 cellular and the multicellular types of structure (see p. 1 13). 



