282 THE PROTOZOA 



with a small fusiform micronucleus lying close to it. It has only been reported 

 once for man. 



SPOROZOA 





This class of Protozoa gets its name from the method of reproduction 

 sporulation. These parasites rarely show binary fission. While 

 the sporozoa are found within cells, in the tissues and in internal cavi- 

 ties, as intestine and bile ducts, yet it is as inhabitants of the blood that 

 they have their greatest importance for man these are known as 

 Haemospbridia. A sporozoon may be either naked or amoeboid or be 

 covered with a distinct cuticle. 



NOTE. Sporozoa are divided into two subclasses the Telosporidia and the Neo- 

 sporidia. In the former the vegetative activity of the protozoon goes on to full 

 growth at which time the reproductive activity commences. With the Neosporidia, 

 however, the growth and reproduction go on at the same time. 



Among the Telosporidia we have the orders Gregarinaria, Coccidiaria, and 

 Haemosporidia. 



Gregarines are chiefly parasites of arthropods and worms and are not known for 

 man or the higher vertebrates. 



The subclass Neosporidia is practically of no importance in human parasitology, 

 only the order Sarcosporidia having been reported for man. From an economic 

 standpoint, however, the order Myxosporidia is of great importance Nosema 

 bombycis being the cause of pebrine, a disease destructive to the silkworm. 



Coccidiaria 



The parasites of the order Coccidiaria are almost exclusively found in 

 the intestines and in the organs connected with it. In the vegetative 

 stage it lives within an epithelial cell, which it destroys. Afterward 

 it falls into the lumen lined by this epithelial cell and sporulates, either 

 by the method of schizogony or sporogony. 



Owing to their egg-like shape, coccidia have often been considered as the ova of 

 intestinal parasites, and vice versa. Upon swallowing an oocyst with its contained 

 sporozoites the membrane of the oocyst is digested in the duodenum and the sporo- 

 zoites liberated. They enter epithelial cells, as of intestine, and reproduce by 

 schizogony. After a varying number of nonsexual cycles sporogony commences, 

 sporonts being produced instead of schizonts. The female sporont is fertilized by 

 the microgamete which is an elongated body provided with two flagella. These 

 microgametes are formed from the male sporont and when thrown off from the 

 periphery they enter (usually a single one) the macrogamete. After fertilization a 

 resistant membrane is formed and the term oocyst is used. Within the oocyst 

 are found smaller cysts, the sporocysts, in which the sporozoites are formed. 



The cycle is very similar to that of malaria except that no arthropod host is 



