The Life History of Tillina Magna 391 



varies in its staining reactions. At one time it may be filled with 

 a vesicular achromatic ground substance in which are embedded 

 many large deeply stained chromatin masses, which often take 

 the form of threads or loops (Text Fig. 3, a ^ r) . Another individual 

 may have a nucleus in which the achromatic material is faintly 

 stained, and in which there is no indication of the presence of 

 chromatic material having lost its power of taking the nuclear 

 stain The micro-nuclei are small spherical bodies 5// in size, 

 situated close to the macro-nucleus, either embedded in the larger 

 nucleus, or at the edge. The homogeneously staining chromatic 

 mass is surrounded by a clear non-staining area which separates 



Fig. 2 Types of nuclei. These may be transition stages between the normal elipsoidal nucleus and 

 the spherical nucleus of the division cyst. X 400. 



SI" 



i'.i-V^' 



y a 



Fig. 3 Sections through the normal elipsoidal nuclei showing characteristic appearances of the 

 chromatic substance. 



it from the membrane always present. They vary from four to 

 ten in number. Many times I have found two in close proximity, 

 indicating a late division. Once only I found what seemed to be 

 a spindle formation. The bodies are so small that it is impos- 

 sible to distinguish the internal structure. 



Intracellular digestion in Protozoa has long been a disputed 

 question. Engelmann ('79) and Le Dantec ('92) concluded from 

 their experiments that the digestion was due to the presence of 

 an acid medium. Mouton and Mesnil ('90) came to the opposite 

 conclusion. Greenwood ('94) made extensive experiments on 

 the digestion of the gastric vacuoles in Carchesium, and came to 

 the conclusion that the original vacuole is not the digestive vacu- 



