1-74 FLEAS, FLUKES AND CUCKOOS 



globular form when at rest. Amoebae move and eat their food by 

 means of pseudopodia. Part of the cytoplasm is pushed outwards until 

 it protrudes like a finger. Then the rest of the body flows into it and 

 thus the organism can move slowly from one place to another. By 

 means of these pseudopodia they also encircle particles of food such as 

 bacteria, cysts of other Protozoa or blood corpuscles and subsequently 

 ingest them. Owing to the fact that these naked blobs of protoplasm are 

 the first living animal the average naturalist examines under the micro- 

 scope, they are, to most of us, objects of great affection and nostalgic 

 pleasure. 



Although most amoebae are free-living in soil and water, the 

 majority of vertebrate animals harbour either commensal or parasitic 

 forms in their large intestine. In man there is one highly pathological 

 species which lives on red blood corpuscles and is the cause of so-called 

 amoebic dysentery. The only family which includes important bird 

 parasites is the Amoebidae (Fig. 2,i). The best known British species 

 from \vild birds is Entamoeba lagopodis from the intestine of the grouse. 

 iMultiplication occurs by binary fission. The organism elongates and 

 then splits in two. Cysts with four nuclei are formed and these pass 

 out of the grouse with the faeces. They contaminate drinking water and 

 food and are thus ingested by new hosts. The amoebae themselves can- 

 not survive outside the body. 



Various other species have been described, from fowl, domestic 

 ducks and geese, and certain wild birds, with cysts showing one, four 

 or eight nuclei. 



The foregoing account of the Protozoa from birds scarcely does the 

 group justice. A great deal has to be compressed into a small space, the 

 terminology is necessarily technical and the subject matter so compli- 

 cated that little more than a straightforward factual account can be 

 given. Undeniably the chapter makes dull reading. To dispel this im- 

 pression Protozoa have only to be looked at alive under the microscope. 

 Most people instantly fall under their spell. The great majority of these 

 organisms are colourless and in studying them one enters a fascinating 

 world of relative transparencies. Every species displays some subtle 

 difference in opaqueness, density, refraction or translucence. Protozoa 

 move in countless different ways. Some dash across the field of vision 

 like express trains, some corkscrew around in never-ending spirals, 

 some flicker intermittently like summer lightning, others swim by the 

 rhythmical beating of countless transparent ciha, or lash their way 



