402 BIOLOGY OF THE PROTOZOA 



Reichenow in making them an independent order which he calls 

 the Entodiniomorpha. These are all peculiarly differentiated gut 

 parasites of mammals in which the cilia are reduced and represented 

 only by the adoral zone of membranelles which runs into a deep 

 vestibule at the anterior end of the body (Fig. 2, p. 20). The pos- 

 terior end is often drawn out into characteristic processes (Fig. 140, 

 ]). 293). In Cycloposthium and related genera (see Key, p. 515) 

 there are bundles of cirrus-like motile organs in addition to the 

 adoral zone, the various arrangements of these groups of motile 

 organs furnishing the basis for generic distinctions (see Key, p. 513). 



THE MORE IMPORTANT SPOROZOAN PARASITES OF MAN. 



The Sporozoa comprise a most heterogeneous collection of animal 

 parasites with hosts in every branch of the animal kingdom, and 

 to limit their discussion here to the parasites of man is entirely a 

 matter of expediency. 



We follow Doflein in giving a broader interpretation of Leuckart's 

 group Sporozoa than does Wenyon. The latter separates the 

 Cnidosporidia as a distinct Class from the Sporozoa in which he 

 includes only the Gregarinida and the Coccidiomorpha. These two 

 groups are united here as Orders in the Sub-class Telosporidia, 

 Schaudinn, while the Cnidosporidia (Schandinn's Neosporidia) con- 

 stitute an equivalent sub-class, but without any obvious relation- 

 ship to the Telosporidia. With the possible exception of Sarcocystis 

 which still has an uncertain taxonomic position, none of the Cnido- 

 sporidia are parasites of man. 



In a discussion of human sporozoan parasites we are limited, 

 therefore, to the Telosporidia comprising the Gregarinida and the 

 Coccidiomorpha. The former are coelozoic parasites of inverte- 

 brates; the latter are parasites of both invertebrates and vertebrates 

 and are much more harmful to their hosts than are the gregarines. 

 This is due to their characteristic cytozoic mode of life which 

 involves the active destruction of tissue cells with corresponding 

 weakening of functions. These are the only forms of Sporozoa 

 which man has to fear and relatively few of them are known to 

 cause human disease. 



According to the site of infection the Coccidiomorpha are divided 

 into Coccidia, or tissue-cell-dwelling forms, and Hemosporidia, or 

 blood-cell-dwelling forms. Notwithstanding the difference in habi- 

 tat and the special adaptations which are characteristic of blood 

 parasites, there is a remarkable uniformity in the life histories of 

 all coccidia and hemosporidia, and a common terminology has been 

 adopted for the different stages. The life cycle of Eimeria schubergi, 

 as given by Schaudinn for the parasite of the centipede, IAthobius 

 forftcatus, although thirty-two years old, is still the clearest and 



