544 BIOLOGY OF THE PROTOZOA 



They cause epidemic diseases, particularly in cattle (e. (/., Texas 

 fever. East Coast fever, etc.). Here, as in Hemosporidiina, there 

 are two families— Babesiidae and Theileriidae, differing again in 

 the site of the asexual cycle. In Babesiidae the parasites reproduce 

 only in red blood corpuscles and only a limited number of division 

 products are formed. In Theileriidae schizogony occurs in endothe- 

 lial cells where a large number of merozoites are produced. 



Order 2. Adeleida. 



The members of this order differ from the Eimeriina in the 

 absence of flagellated gametes and fertilization of the Eimeria type. 



A b 



Fig. 217. Adelina dimidiata A. Schn. A, association of macrogametocyte and 

 smaller microgametoeyte. B, nuclear divisions in microgametoeyte and formation 

 < if gametic nuclei. X 1400. (From Dofiein after Shellack, Arbeit, aus d. kaiserlichen 

 Gesundheitsamt, courtesy of J. Springer.) 



In place of this the sexual process resembles that of pseudo-conjuga- 

 tion in gregarines, without, however, the formation of a gametocyst 

 or a double set of gametes. Two gametocytes, one of which is 

 smaller, unite as in pseudo-conjugation. The microgametoeyte may 

 rest cap-like over one pole of the macrogamete (as in Adelea), or 

 laterally (as in Adelina, Fig. 217). The nucleus of the microgameto- 

 eyte divides one to three times and one of the products enters the 

 macrogamete and fuses with its nucleus. A rigid fertilization mem- 

 brane— oocyst- as in Eimeria, is formed in species of the sub- 

 order Adeleina, but in the sub-order Hemogregarina the oocyst is 

 delicate and like that of Plasmodium enlarges with growth and 

 development of the zygote. Species of Adeleina are intestinal para- 

 sites and infection is contaminative. Ilemogregarines are blood 



