PROTOZOA 173 



axostyle supporting the body^ several free anterior flagella and an 

 undulating membrane bordered by a marginal flagellum. They divide by 

 simple fission and no sexual phenomena have been observed. They do 

 not form cysts but remain alive long enough outside the body to effect 

 successful transference to new hosts. In the intestine of various birds, 

 species like Trichomonas gallinarum ingest debris, bacteria and other solid 

 particles and are apparently harmless, although on rare occasions they 

 invade the liver with disastrous consequences. A species, T. gallinae, 

 from the mouth, throat and oesophagus of birds such as gulls, falcons, 

 pigeons and poultry, appears to consume leucocytes and attacks the 

 mucous membrane, and T. columbae, from the crops of pigeons, is 

 closely related to a species found in the vagina of Homo sapiens. 

 Another related species, T. foetus, infecting the uterus and penis of 

 cattle, is an important cause of abortion in cows. 



Other flagellates found in the intestine of birds include forms such 

 as Chilomastix gallinarum (Fig. 2,e) from the caecum of the fowl and 

 Cochlosoma anatinis from the intestine of mallard, shoveller, pintail, scaup 

 and other duck. 



Order Diplomonadida 



The flagellates from this order are strikingly different from all the 

 others. Owing to a duplication of certain organs they are bilaterally 

 symmetrical. This gives the impression that the animal is in the process 

 of longitudinal fission. 



Giardia (Fig. 2), which is the best known genus, superficially re- 

 sembles a pear split in half, with eight flagella arranged in pairs arising 

 from different parts of the body. It clings to the epithelial cells lining 

 the small intestine by means of a sucking disc. Apparently it stimu- 

 lates a copious secretion of mucus upon which it subsequently feeds. 

 Intermittently it forms cysts which pass out in the faeces and are thus 

 transported to other hosts. Giardia is found in vertebrate animals 

 throughout the world and has been recorded from a variety of bird 

 hosts including the common buzzard, shrike, avocet and several species 

 of herons. The allied genus Hexamita has also been recorded from birds. 



Class Rhizopoda 

 This class comprises some of the simplest Protozoa known as amoe- 

 bae. The body has no definite shape or orientation, but assumes a 



