ISS PROTOZOA 



That always gametes of different eirigia fuse is shown liy Slylorliyiicluis 

 where the gametes of one animal are llagellate, those of another are station- 

 ary. Tills dlmorpliism is so great in the AggregaUe thai hliform spermato- 

 zoids occur, as in the Coceidia. After the formation of the gametes the 

 moyenients of the residual Ijody bring about the expulsion of the pscutlo- 

 nayicelUr; and in many Gregariircs sporodHcIs are present lor their 

 escape. With repeated formation of a residual l)ody, the contents of the 

 pseudonayicella diyides into (usually eight) sporozoilcs or fah-ifonii spores, 

 which must leaye the spores and pass anew into the tissue cells in order to 

 form gregarines. Tliis escape of the sporozoites depends upon entrance 

 into the proper host. Often the transformation of the contents of the 

 c\'sls into pseudonayicelbe takes place when the cysts haye left the original 

 host. 



Best known arc the Monocvslis Icnax of the spermatlicca of earthworms, and 

 CI''t>siili'iiia hhillanun of the cockroach. The American species have scarcely 

 been touclred. 



Order 11. Coccidiae. 



Of all Sporozoa the gregarines are nearest the Coccidiae, which are also eel! 

 parasites with a single nucleus, but without either cell membrane or division into 

 protomerite and deutomerite. Best known is Eimcria slicdcc (also called 

 Coccidium cu-nicuU and ovifoniic), parasitic in the liver and intestinal epithelium 

 of mammals. In the progamic development the fully grown parasite (fig. 146, 

 2) divides inside the infected cell into many cells (3, 4, 8); these separate, infect 

 other cells and begin growth and division anew (autoinfectionh After this is 

 repeated several times fertilization appears (^), some parasites giving rise to 

 macrogametes, others by division forming small, actiyelv swimming micro- 

 gametes with one or two flagella. The fertilized macrogamete or zygote (0, 7, 

 9, 10) encysts, passes out and serves to infect a new animal. Beginning earlier 

 or later, but only concluded in a new host, the contents of the cyst divide into 

 several (in Eimcria, four) sporoblast-containing spores. Each spore (7, it) 

 forms one or several (Eimcria, two) sporozoites, a residual body being left 

 behind (r). Eimcria slicda produces cheesy granules in the liver of mammals. 

 It is common in rabbits, rare in man. In cattle it is the cause of red dysentery. 



Order III. Haemosporida. 



The Ha;mosporida arc very similar in structure and development to the 

 Coceidia. They live in blood corpuscles, and on this account and from some 

 analogies not sufficiently understood, they are regarded as related to the Try- 

 panosomes. The hhemamoebal forms parasitic in man cause malaria, there 

 being in these a progamic reproduction with autoinfection and a metagamic 

 in which the disease is transferred to another host. The parasites in the blood 

 corpuscles (fig. 147, 1-3) grow and divide (daisy form, 2), characterized by 

 little accumulations of pigment derived from the haemoglobin of the corpuscle. 

 These division products are set free by a breaking down of the cor]niscle 

 (period of chill) and infect other corpuscles. This autoinfection can continue 

 a long time, until the FLTmamccbx in the corpuscles grow, without dividing, to 

 'half moons' (4); these either become round and form macrogametes (5) or divide 

 into eight microgamctes (6). The conjugation of these seems only to take place 



