Two other species, _P. rudis_, Diesing, 1850, in a Brazilian otter (_Lutra brasiliensis_) and _P. compactus_, Cobbold, 1859, in the Indian ichneumon, are but little known. _Habitat._--Lungs, pleuræ, and especially the bronchi of man and dog. The alleged occurrence (of eggs) in other organs may be due to confusion with those of _Schistosoma japonicum_. _Distribution._--China, Korea, and especially in Japan, where, according to Katsurada, there are no districts that are entirely free from pulmonary flukes. The _mountainous_ provinces of Okayama, Kumamoto, Nagano and Tokushima are the principal centres. [Illustration: FIG. 151.--Egg of _Paragonimus ringeri_, Cobb., from the sputum. Showing the ovarian cell and vitelline cells and granules. 1,000/1. (After Katsurada.)] _Pathology._--The number present in the lung varies from two to twenty, about. Usually one cyst contains one worm, but in the dog each cyst contains two. The cysts admit the tip of the finger, and have a fibrous wall 1 mm. thick. They originate partly from dilatation of bronchi and bronchioles. Others arise from the inflammatory reaction of lung tissue into which the worms have wandered. The worms and their eggs cause bronchitis and peribronchitis, catarrhal, hæmorrhagic, or purulent, and areas of consolidation. Areas containing eggs in their centre resembling tubercle nodules are not uncommon, and extensive cirrhosis of the lung may be found. As a result of these changes, emphysema and bronchiectasis also occur. As to the development, only the following details are known: that the eggs, which before segmentation of the ovum reach the open in the sputum and through being swallowed also in the fæces, develop in water into a miracidium ciliated all over, which hatches and swims about freely. According to Manson this takes place in four to six weeks. Sub-family. *Opisthorchiinæ*, Looss, 1899. Genus. *Opisthorchis*, R. Blanch., 1845. Opisthorchiinæ with lobed testes. Laurer’s canal present. Parasitic in the bile-ducts of mammals and birds. *Opisthorchis felineus*, Riv., 1885. Syn.: _Distoma conus_, Gurlt, 1831 (_nec_ Creplin, 1825); _Distoma lanceolatum_, v. Sieb., 1836, v. Tright, 1889 (_nec_ Mehlis, 1825 = _Fasciolo lanceolata_, Rud., 1803); _Distoma sibiricum_, Winogr., 1892; _Distoma tenuicolle_, Mühl., 1896.