NEMATODA. 289 



Diesing into numerous genera. F. (Dracunculus) medinensis* Gmel. the Guinea 

 worm, in the subcutaneous cellular tissue of man in the Tropics.of the Old World, 

 reaches a length of two feet or more. The head is provided with two small 

 and two larger papillae. Alimentary canal degenerate. The female is vivipa- 

 rous, and without sexual opening. The male form is unknown. The worm 

 lives in the connective tissue between the muscles and beneath ttte skin, and 

 after reaching sexual maturity, occasions the formation of an abscess, with the 

 contents of which the embryos escape to the exterior (Fig. 236). It has lately 

 been proved (Fedschenko) that the embryos of Filaria migrate into a Cyclops 

 and there undergo an ecdysis. Whether they are then (in the body of the 

 Cyclops) introduced into man in his drinking water, or whether they first escape 

 and copulate in a free state, is not known. F. immitis lives in the right 

 ventricle of the dog, and is very abundant in East Asia. It is viviparous. 

 The embryos pass directly into the blood, where, however, they do not undergo 

 their further development. Similar immature Filariae are also found in the 

 blood of man in the Tropics of the New and Old Worlds, and havB been 

 described as F. sanguinis hominis nocturna, the sexual form living in the 

 lymphatic glands as F. Bancrofti Cobb. The intermediate host is probably the 

 mosquito, on the death of which the larvae make their way into the water in 

 which they, presumably, enter the alimentary canal of man. It is supposed 

 that they make their way from the alimentary canal, by active migration, to 

 the lymphatics where they mature and pair, f The larvae enter the blood and 

 probably escape by means of abscesses, etc., and by the kidneys, since they are 

 also found in the urine ; their appearance seems to have an aetiological con- 

 nection with chyluria and elephantiasis. F. sanguinis hominis nocturna is 

 periodic, appearing only in the blood at night. Two other varieties of Filaria 

 are also found in the human blood, viz. diurna which appears in the day, and 

 perstans. Filaria perstans is supposed to have a connection with the sleeping 

 sickness of negroes. The sexual forms of F. diurna and perstans are unknown. 

 In the East Indies, young Filaria also live in the blood of the street dog, and 

 would seem to be related to the brood of Filaria sanguinolenta, since, according 

 to Lewis, knotty swellings on the aorta and oesophagus are invariably found 

 with these Filaria. F. papillosa Hud. in the peritoneum of the horse. F. loa 

 Guyot., in the conjunctiva of negroes on the Congo. F. labialis Pane, only 

 once observed at Naples. An immature Filaria described as Filaria lentis (oculi 

 humani) has been found in the human capsula lentis. Ichthyonema Dies. , anus and 

 vulva absent, male minute, in fishes. Spiroptera Rud., S. obtusa Rud., stomach 

 of mouse, asexual larva in meal-worm. Spiroxys Schn., Hystrichis Molin ; Tetra- 

 meres Crepl. ( Tropidocera Dies. ) ; Hedruris Crepl. ; Ancyracanthus Dies. 



Fam. 5. Mermithidae. Aproctous Nematodes, with very long filiform body, 

 and six oral papillae. The male caudal region is broad, and is provided with 

 two spicula and three rows of numerous papillae. They live in the body-cavity 

 of insects, and escape into the damp earrtli, where they attain sexual maturity 

 and copulate. Mermis nigrescens Duj. was the occasion of the fable of the 

 rain-worm. M. albicans v. Sieb. v. Siebold established by experiment the 

 migration of the embryos into the caterpillars of Tinea evonymella. 



* Compare H. C. Bastian, " On the Structure and Nature of the Dracunculus," 

 Trans. Linn. Society, vol. xxiv., 1863. Fedschenko I.e. 



t P. Hanson, China Customs Report, No. xiv., 1878. T. Lewis, Q.J.M.S., 

 19. 1879. See also Hanson, in Davidson's "Hygiene and Diseases in Warm 

 Climates" London, 1893. 



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