218 



NEMATHELMINTHES 



grows until it is many times the size of the rest of the worm, reaching 

 a length of 15 mm.; the young larvae are born in the bee. 



6. TYLENCHTJS Bastian. Cuticula ringed; body tapering to a point 

 behind; mouth with a spine for piercing plant tissues; vulva much back 

 of the middle: numerous species, which are parasitic in plants. 



T. tritici Bast. Male 2 mm., female 4.5 mm. long and spirally 

 rolled together; color yellowish: in wheat, in a grain of which several 

 larvae may live; when the wheat is sown the larvae migrate into the 

 young plants and finally become mature in the buds; 

 the eggs are laid here and the young larvae migrate 

 into the ripening grain and remain there; they can lie 

 in dried wheat for years without dying. 



7. STRONGYLOIDES Grassi. Minute worms with 

 heterogony, a non-parasitic, unisexual generation alter- 

 nating with an hermaphroditic parasitic generation, the 

 former having a very long cylindrical oesophagus, the 

 latter with a short oesophagus with a bulb; no teeth 

 and 2 spicules present: 1 species. 



S. ster cor alls* (Bavay) (Fig. 348). Hermaphro- 

 ditic form (S. intestinalis Bavay) 2.2 mm. long and 

 .034 mm. wide, with an oesophagus a quarter as long as 

 the body ; vulva in the hinder part of the body : it lives 

 in the human intestine and causes Cochin China diar- 

 rhoea, having been first observed in that country; a few large eggs are 

 produced, from which hatch rhabditiform larvae, which are about .3 mm. 

 long; they pass out with the feces and develop into the unisexual form, of 

 which the male is .7 mm. and the female is about 1 mm. long, and which 

 lead a free life; from their eggs the parasitic generation develops; in 

 this country and Europe only the parasitic generation is known. 



FAMILY 3. MERMITIDAE. 



Hairworms. Body long and filiform; mouth with 6 papillae; adults 

 Without anus; hinder part of the intestine solid; male with 2 spicules 

 and 3 rows of papillae: the young animals live in the body cavity of 

 insects, especially caterpillars, grasshoppers, and beetles, and occasion- 

 ally spiders and snails or crayfish, from which they migrate into the ground 

 or the water; here they become mature and lay their eggs; 1 genus. 



MERMISJ Dujardin. With the characters of the family: several 

 species. 



* See "Occurrence of Strongyloides intestinalis in the United States," by M. L. 

 Price, The Jour, of the Am. Med. Asso., Vol. 41, 1903. 



t See "Observations," etc., by J. Leidy, Proc. A. N. S., Phila., Vol. 5, p. 262. 

 "A Synopsis of Entozoa," etc., by same. Ibid., Vol. 8, 1856, p. 42. 



Fig. 348 

 Strongyloides 

 stercoralis 

 (Braun). 

 A, hermaphro- 

 ditic form 

 B, larva. 



