IV 



VEEMESS Y STEM A TIC RE VIE W 



179 



B 



muddy earth. Sexes separate. The females are viviparous, and produce only a few 

 young (4 at most), which, after being hatched, find their way into the lungs of 

 frogs and toads, and there 

 develop into mature her- 

 maphrodite animals (Ascaris 

 ii/i/rovciiosit), from whose fer- 

 tilised eggs the free - living 

 Rhabditis generation again 

 arises. The life-history thus 

 exhibits a sort of heterogeny. 

 SpJuerularia bombi, the Rhab- 

 ditis - like young form lives 

 in the earth. The fertilised 

 females find their way into 

 the female humble bee, where 

 they are parasitic in the body 

 cavity or in the intestine. 

 The uterus, which is filled 

 with embryos, soon begins to 

 hang out from the female 

 genital aperture, and becomes 

 a large pouch, to which 

 the worm-body finally forms 

 merely a small insignificant 

 appendage. Mermithidce, with- 

 out anus. The young are 

 parasitic in the body cavity 

 of Insects ; they make their 

 way out into damp earth, 

 where they become sexually 

 mature and reproduce them- 

 selves ; Mcrmis nigrcscens. 



Filariidce : Filaria mcdin- 

 ensis (medina worm), may 

 have a breadth of 0'5-2 mm. 

 and length of nearly a metre ; 

 in the subcutaneous connec- 

 tive tissue of man, in warm 

 regions of the Old World. 

 The young in small Crustacea 

 (Cyclopidce). Trichotrachclidce: 

 Trichocephalus dispar, with 

 swollen hinder body, in the 

 human csecum. 



Trichina spiralis (Fie FlG ' 121. Trichina spiralis (after Claus). A, Encysted 



121 ) lives sexually mature mUSCle T hina ; "</' altered muscle fibres ' / fet g lobules ' 



J . . cy, cyst; bk, envelope of connective tissue. B, Female intes- 



so - called intestinal tinal Trichina ; ov, ovary ; e, embryos ; zk, cell bodies (in the 



Trichina in the small intestine post cesophageal division of the intestine) ; wo, female aperture. 



of man and in that of many c > Male intestinal Trichina; a-, oesophagus; 7i, testis ; de, 



mammals ; is viviparous ; the ductus e J aculatorius - 



female (B) is ca. 3 mm., the male (C] half as long. The young bore their way 

 into the intestinal wall, pass from here through the body cavity, or with the blood 



