The male measures 83 mm. in length by 0·28 to 0·40 mm. in breadth. The anterior extremity is rounded, and has no papillæ (?6); the posterior extremity exhibits a double curve, with four pre-anal and four post-anal papillæ on each side. These are large and have a villous appearance. The mouth is round and unarmed, the pharynx measures 1 mm. in length, is cylindrical, very muscular, and its hinder part is dilated. The anus is situated 0·11 mm. in front of the hind end. There are probably two unequal spicules; one only, however, is known—apparently the shorter one—the length of which is given as 0·17 to 0·23 mm.
The female measures 155 mm. in length and 0·6 to 0·8 mm. in breadth; the rings of the cuticle are 0·005 mm. apart (in the male 0·003 mm. apart); the anterior extremity is slightly thickened and club-like, the posterior extremity is slender, and terminates obtusely; the lateral line is 0·127 mm. in breadth (that of the male 0·007 to 0·008 mm.); the anus opens 0·13 mm. in front of the hind end, the vulva is 2·5 mm. distant from the mouth, the ovaries are two much convoluted tubes. The eggs measure 38 µ by 11 µ.
This species was first discovered at a post-mortem, in the left ventricle, by J. P. Figueira de Saboia in Rio de Janeiro, and has been described by P. S. de Magalhães.
D. immitis occurs in the right ventricle of the heart of the dog in Europe and the Tropics.
D. repens is also a common subcutaneous Nematode in dogs in Annam.
Sub-family. Onchocercinæ, Leiper, 1911.
Cuticle with spiral thickenings.
Genus. Onchocerca, Diesing, 1841.
Male with four pre-anal papillæ. Female with vulva situated anteriorly.
Onchocerca volvulus, R. Leuckart, 1893.