IV 



VERMES SYSTEMATIC REVIEW 



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 

 nigrovcnosa}, from whose fer- 

 tilised eggs the free -living 

 Rliabditis generation again 

 arises. The life-history thus 

 exhibits a sort of heterogeny. 

 Sphcerularia 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 ; Mermis nigrescens. 



Filariidce : Filaria medin- 

 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}. Trichotrachelidce: 

 Trichocephalus dispar, with 

 swollen hinder body, in the 

 human csecum. 



Trichina spiralis (Fig. 

 121) lives sexually mature 

 as the so - called intestinal 

 Trichina in the small intestine 

 of man and in that of many 

 mammals ; is viviparous ; the 

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

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



FIG. 121. Trichina spiralis (after Glaus). A, Encysted 

 muscle Trichina ; mf, unaltered muscle fibres ; /, fat globules ; 

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

 tinal Trichina ; ov, ovary ; e, embryos ; zk, cell bodies (in the 

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

 C, Male intestinal Trichina ; cc, oesophagus ; h, test-is ; de, 

 ductus ejaculatorius. 



