308 



GRIFFIN. 



Fig. 11- 



cestej'i showing the 

 meganucleus over the pharynx 



Tlie megan\icleiis lies close to tlie \entral surface of the body. In order 

 to pass the phar\'nx, it bends over 

 the dorsal side of this organ, as 

 shown in test figure 11. 



The chromatin of the meganucleus 

 is arranged in a fine reticulum, as 



Lateral view of E>^plote. war- ^^ ^^O^^'^ ^y ^"^^^^ I^, figures 1, 2, 



curvature of the 3, and -t. It is generally found that 

 the fibers of the reticulum on the 

 anterior side of the anterior enlargement of the meganucleus are greatly 

 attenuated, causing that part to appear less deeply stained than others. 

 The nucleus is rarely visible in living animals. If the Euplotes are in 

 a very clear, transpiarent condition, the meganucleus can sometimes be 

 seen and its structure examined with an immersion lens. Under these 

 circumstances the granular reticulation and clear, fluid ground-substance 

 can be seen, the structure appearing the same as in the stained specimens. 

 At times when division is common and the animals seem to be well 

 nourished and normal in everj' way, the interior of the nucleus of many ^ 

 animals becomes vacuolated. The vacuoles increase in size until all the 

 protoplasmic portion of the nucleus is crowded into a layer along the 

 nuclear membrane, while the interior consists of one or several large 

 vesicles of clear fluid. It is only when in this condition that the nucleus 

 is easily visible in the living- animal. As the vacuoles increase in size 



Fig. 12. — Sl;etch of a vacuolated : 



anucleus, drawn from the living 



