CHAPTER IV 



OPALINA I MONOCYSTIS PARASITES BIOGENESIS AND ABIO- 



GENESIS CLASSIFICATION OF THE UNICELLULAR 

 ORGANISM EXAMINED. 



AMONGST the Protozoa (see p. 220) are found certain forms 

 which are parasites. Parasites are organisms which live in 

 association with other organisms, the ready-digested food of 

 which they utilise or even nourish themselves from the 

 tissues of the forms they infest. It will be interesting to 

 compare Paramcecium with a ciliate infusor which lives 

 in the intestine of the common frog, and is known as 

 Opalina ranarum. 



' Opalina has a flattened body with an oval outline (Fig. 73, 

 A, B), and full-sized specimens may be as much as i mm. 

 in length. The protoplasm is divided into cortex and 

 medulla, and is covered with a cuticle; the cilia are equal- 

 sized and uniformly arranged in longitudinal rows over the 

 whole surface. 



On a first examination no nucleus is apparent, but after 

 staining, a large number of globular nuclei can be seen (B, nu) : 

 these nuclei multiply within the body of the infusor. 



The presence of numerous nuclei in Opalina is a fact 

 worthy of special notice, The unicellular organisms we have 



