12 



Fig. 12), a womilike creature of doubtful affinities, which 

 usually takes up a position in the lungs of its host. 



Molluscs frequently contain the immature stages of 

 Teematodes. 



Insects, such as beetles, grasshoppers and flies, often 

 harbour the immature stages of " Haib-\yokms " (Gordius 

 and a Nematode worm of somewhat similar appearance, 

 Mermis). These live coiled up in the body-cavity of the 

 host. It is to be desired that the adult stages of these 

 worms should be obtained, and if possible some knowledge 

 acquired as to their eggs and larvae, and the mode of 

 infection of new hosts by the larvte. It is recommended, 

 therefore, that when these worms are seen emerging from 

 insects, or found crawling about, an attempt should be 

 made to keep them alive for a time in damp earth, water, 

 etc., in the hope of learning more of their life-history, as 

 the mature stage is usually only reached after leaving the 

 insect host. Some small Nematodes are also parasitic 

 in insects, but usvially require the microscope for their 

 detection. 



{b) Fresh-water worms. 



TuRBELLAKiA are connnonly found in any standing 

 water, crawling on water- weeds or on the bottom, or even 

 upside down on the surface-film. Since many of them 

 are carnivorous, and have a liking for decaying matter, 

 they may sometimes be conveniently caught by sinking a 

 pot of dead earthworms in a pond or ditch, drawing it up 

 after a day or two and collecting the Planarians that have 

 been attracted by it. 



Fresh-water fishes,* amphibians, etc., as mentioned 

 above, should be examined for parasites. Some of the 

 Insects and Crustacea also harbour Nematodes and 

 Nematomoepha. 



Nemeetinea are rare in fresh water, but may be 

 found occasionally. 



Many Nematoda occur in fresh water, in the mud at 

 the bottom, or among plants, but these are chiefly of 

 microscopic size. 



Nematomoepha habitually pass their adult stage of 

 existence in fresh water, sometimes in standing water, 

 sometimes in quite rapid streams. They may often be 



* Fishes frequently harbour parasitic Crustacea, especially on their gills. 

 These parasites should, if possible, be preserved, with a note of the position in 

 ■which they were found, and information about the " host." 



