136 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



vertebrate animals. They are a very important order. The genus 

 Plasmodium causes malaria in man (page 832); while Proteosoma and 

 HcRm,oproteus are malarial parasites of birds (page 832). The Hcemogre- 

 garince are usually harmless parasites of reptiles and batrachians 

 (frogs) ; a part of their life is passed within the red cells of their host, 

 but they have a slowly moving stage, somewhat resembling a gregar- 

 ine, which occurs free in the blood. Hepatozoon perniciosum is the 

 best known of a group of haemogregarine-like parasites which are 

 parasitic, often within the white cells of the blood, in dogs, in rats, and 

 in other rodents; so far as is known, they do not cause disease. The 

 genus Babesia (page 836) includes parasites which cause important 

 diseases in cattle, sheep, horses and dogs. Similar parasites have 

 been found in the blood of monkeys, of dogs, of rats and other rodents. 

 The Sarcosporidia are tube-like in shape and filled with spores. They 

 are found within the cells of the voluntary muscles. The Haplosporidia 

 are a group of very small sporozoa of which little is known. Some of 

 them are parasitic in fish; one of them, Rhinosporidium kinealyi, has 

 been found in a tumor of the nose of a native of India. The Myxo- 

 sporidia (page 841') are recognized by the peculiar form of their spores; 

 each spore has one or more capsules each furnished with a coiled fila- 

 ment or thread which is extruded under certain conditions and probably 

 serves to anchor the spore to a surface upon which further development 

 may occur. Members of this order are parasitic in various tissues of 

 > fishes and they often produce disease in their hosts. The spores of the 

 Microsporidia (page 841) are exceedingly small; a member of this 

 order is the cause of pibrine in silk-worms (page 656). 



The INFUSORIA (page 841) are a large class. Most of them are not 

 parasitic. They are the most highly developed of the protozoa and 

 their bodies are more or less covered with cilia, by which they move 

 themselves through the liquids in which they live. 



In the last class, under the heading Parasites of Uncertain Position, 

 are grouped a number of organisms which cannot be classified because 

 so little is known of them at present. Histoplasma capsulatum{-pa.ge 

 842), the Chlamydozoa (page 842) and the Ultramicroscopic viruses 

 (pages 116, 842) are all associated with important diseases in men and 

 in animals. 



The SPiROCH^TiE (page 843), as their name signifies, are thread-like 

 organisms, which seem to be coiled in a spiral. It is probable that the 



