270 



OrALINA 



presents a condition of things intermediate between the 

 unicellular and the multicellular types of structure. 



Fig. 71. — Opal'uia rniitxriun. 



A, livint; specimen, surface view, showing longitudinal rows of cilia, 



B, the same, staini.-il, showing numerous nuclei («?(■) in various stages of d 



C, I — 6, stages in the division of a nucleus. 



D, longitudinal fission, 



E, transverse fission. 



F, the same in a specimen reduced tn si;;e hy repeated division. 

 Ci, final product of successive divisions. 



H, encysted form. 



I, uninucleate form produced from c>st. 



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

 A— C, after Pfitzner ; D— K, from Saville Kent, after Zeller.) 



biology : 



There is no contractile vacuole, and no trace of either 

 mouth or gullet, so that the ingestion of solid food is impos- 

 sible. The creature lives, as already stated, in the intestine 



