NEMATODA 



219 



M. nigrescens Duj. (Fig. 349). Body 12 cm. long, .5 mm. thick, 

 attenuated anteriorly and blunt behind; color white, with the black 

 ovary showing through ; the young worms migrate on warm 

 summer days from the body of their hosts, often in large 

 numbers, into the moist earth, causing a belief that they 

 have rained down. 



FAMILY 4. FTLARIIDAE.* Fig. 349 



Mermis 



_i . _ n ,.n ,-,r>, 11 nigrescens 



Body very long and nliiorm; mouth otten surrounded (Siissw. P. 



by papillae or by 2 lips ; no oesophageal bulb ; male with 1 



P^ spicule or with 2 of unequal size and with a spiral twist 



\ of the hinder end; usually viviparous: several genera. 

 FILARIA 0. F. Miiller. Vulva towards the forward 

 end; male with 2 spicules, and much smaller than the 

 female: numerous species, which live in man and other 

 vertebrates as final hosts, and probably in insects or crusta- 

 ceans as intermediate hosts ; Leidy mentions over 30 species 

 in this country. 



F. immitisf Leidy (Fig. 350). Length of male 18 cm.; 

 thickness .9 mm., with a corkscrew hinder end; length of 

 female 30 cm. ; thickness 1.3 mm. : in the heart and veins of 

 the dog, the .28 mm. long larvae appearing in the blood, 

 especially in the night time ; the larvae are transferred from 

 one dog to another by mosquitoes; very common in China 

 and Japan, and occurring in America and Europe ; it some- 

 times infects man. 



F. bancrofti Cobbold (Fig. 351). Male 

 4 cm. long, .1 mm. thick and colorless; 

 female 8 cm. long, .28 mm. thick and 

 brownish in color: in the heart and lymph 

 vessels of man in the tropics, also in the 

 southern United States, the .3 mm. long 

 larvae appearing in the blood, but in the 

 surface circulation only at night ; the larvae 

 are transferred from one person to an- 

 other by mosquitoes; one of the causes of 

 elephantiasis. 



F. loa (Cob.). Male 30 mm. long, .4 mm. thick, with 8 large cir- 

 cumanal papillae; female 41 mm. long and .5 mm. thick; body with 



* See "The Zoological Characters of the Roundworm Genus Filaria," etc., by 

 C. W. Stiles, Bull. 34, Hygienic Lab., etc., 1907. 



t See "Notices of Nematoid Worms," by J. Leidy, Proc. A. N. S., Phila., 1886, 

 p. 308. 



Fig. 350 



Filaria 



immitis 



(from Braun). 



A, male 

 B, female. 



Fig. 351 Filaria bancrofti 



(from Braun), showing 



several worms among 



blood corpuscles. 



