PROTOZOA 379 



Sub-phylum III. Infusoria. Protozoa with cilia. 



Class I. Ciliata. Cilia present at all times. , 



Order 1. Holotrichida. The cilia are distributed over the 

 surface, and there is no specialized oral apparatus 

 known as the "adoral zone" consisting of cilia fused into 

 "membranelles." Here are found some parasites be- 

 longing to the genera Ichthiophthirius, Buetschlia, 

 Anophrys, Isothrica, Dasytricha, Opalina. 

 Order 2. Heterotrichida. With cilia distributed over the 

 general surface, and, in addition, a specialized zone in 

 the mouth-region. Here are several well-known para- 

 sitic forms belonging to the genera Nyctotherus, Balan- 

 tidium, Entodinium, Ophryoscolex and Cycloposthium. 

 Order 3. Hypotrichida. The cilia are limited to the ven- 

 tral surface, and are frequently fused into specialized 

 organs of motion and touch, the cirri. There are no 

 strictly parasitic forms. 



Order 4. Peritrichida. The cilia are greatly reduced, in 

 some cases to the adoral zone, but additional rings may 

 be present. Several ecto-parasites belong here, especi- 

 ally the genera Spirochona, Kentrochona, Lichnophora, 

 Cyclochaeta and Trichodina. 



Class II. Suctoria. Infusoria. Infusoria with suctorial ten- 

 tacles in the place of cilia in the young phases. They are 

 frequently ectoparasites and the young of some genera, 

 e. g., Sphaerophyra, are internal parasites in other infusoria. 

 Sub-Phylum IV. Sporozoa. Protozoa without motile organs; re- 

 production by sporulation; always parasites. 

 Class I. Telosporidia. Sporozoa in which the act of reproduc- 

 tion ends the individual's life, the entire protoplasm being 

 used in forming spores. 



Order 1. Gregarinida. The young stages alone are cell 

 parasites, the adult organisms living in fluids within 

 the cavities of animal hosts. There are no human 

 parasites. 



Order 2. Coccidia. Intracellular parasites, mainly in the 

 epithelial cells of vertebrate and invertebrate hosts. 

 Human parasites have been traced mainly to the genus 

 Coccidium. Here also we should place Cyclasterion 

 scarlatinale Mallory. 



Order 3. Haemosporidia. Sporozoa of small size living in 

 the blood corpuscles of vertebrates. Human parasites 

 belong to the genera Laverania and Plasmodium. 



