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MANUAL OF ELEMENTARY ZOOLOGY 



1. Free-living throughout life. — The Vinegar Worm, Anguillula 

 aceti, found in vinegar. Rhabditis, in soil. 



2. Free as larva, parasitic in plants as adults. — The Cockle Worm, 

 Tylenchus scandens, cause of " ear- cockles " in corn. Small worms 

 from the soil wriggle up the stems of young corn plants, pair in the 

 flowers when these form, cause galls to arise in place of grains, and 

 lay eggs, from which hatch larvae. These can survive dry for twenty 

 years but in damp earth become active. 



3. Free as larva, parasitic in animals as adults. — The Miners' Worm, 

 Ancylostomum duodenale, of a pink colour, the male 8-1 1 mm. long, 

 the female 10-18 mm., lives and pairs in the small intestine of man. 



Fig. 210. — The Vinegar Worm (Anguillula aceti), somewhat dia- 

 grammatic, to show arrangement of organs. 

 A, Male; B, female. 

 t„ Anus ; e., excretory pore ; g.o., genital opening ; int., intestine ; aes.i., bulb of 

 oesophagus ; mi., ovary ; f.s., penial setae ; ph., pharynx ; ;■., testis ; ut., uterus ; 

 zi.d., vas deferens. 



Eggs are passed with the feces of the host and hatch in warm, damp 

 places, but are killed by drought or frost. The little, thread-like laroe 

 pierce the human skin, usually on the foot, hand, or mouth, enter 

 venules, and are carried through the heart to the lung wall, which they 

 penetrate. Thence they reach the gut by way of the glottis. Browsing 

 on the villi, they cause intestinal haemorrhage, and thus aneemia, often 

 fatal. The worm is widespread in warm countries, but elsewhere can 

 exist only where the conditions are favourable, as in mines in Britain. 

 Strict sanitation is necessary for avoiding its ravages. Male fern and 

 thymol are the principal vermifuges used against it. 



4. Larva: parasitic, adults free. — The Rain Worm, Mermis. 

 nigrescens, whose larvse bore through the skin of young grasshoppers 



