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. Tylenchus 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 OBSophagus, the 

 latter with a short oesophagus with a bulb; no teeth 

 and 2 spicules present: 1 species. 



S. stercoralis* (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, o£ 

 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. 



Fig. 348 

 Strongyloides 

 stercoralis 

 (Braun). 

 A, hermaphro- 

 ditic form 

 B, larva. 



Family 3. MEEMITIDAE. 



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 .Tour, of the Am. Mod. Asso., Vol. 41, 190.3. 



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. 



