26 



MORPHOLOGY OF PROTOZOA 



macronucleus alone. Such an amicronucleate race was cultivated by him 

 for several years, during which regular multiplication by fission took place. 

 Abortive attempts at conjugation appeared to be made, but the process 

 was never completed. Landis (1920) has studied a similar race oi Para- 

 mecium caudatum, and Patten (1921) one of Didinium nasutum, while 

 Woodruff (1921a) has described amicronucleate races of OxytricJia fallax 

 and TJrostyla gra?idis. 



P^IG. 



10. — Cysts of E. histolytica from Three Distincx Races ( x 2,200). 

 (After Wenyon and O'Connor, 1917.) 



1-3. Race with exceptionally large cysts 



7-9. Race with small cvsts 



4-6. Race with usual type of cyst. 



CYTOPLASM.— The cytoplasm of the Protozoan cell does not differ 

 in any essential respect from that of cells of multicellular animals. As to 

 the nature of its minute structure many theories have been advanced. 

 That which seems to be most satisfactory is Biitschli's view that cytoplasm 

 is of the nature of an emulsion consisting of at least two substances, 

 one of which in the form of minute globules is suspended in the other, 

 which forms the septa between the globules. In optical section, the 



