A _Bilharzia_, possibly _B. haematobia_, was found by Cobbold in the portal vein of _Cercopithecus fuliginosus_; and _B. crassa_ infests the cattle of Egypt, Sicily, and certain parts of India, but does not produce haematuria. Of the other Trematodes of man and domestic animals there is not room to speak fully. _Distomum pulmonale_, which occurs in the lungs of the cat, tiger, and dog, as well as in man, is especially common in Japan, China, Corea, and Formosa. _D. sinense_ and _D. rathouisi_ have been also found in inhabitants of these countries. BISEXUAL TREMATODES.—Zoologically, _Bilharzia_ is interesting from its bisexual condition. It is not, however, the only bisexual Trematode. In cysts in the branchial chamber of Ray's bream, _Brama raii_, two worms are found, which are probably the slender male and the swollen female of the same species (_Distomum okenii_). The only doubt that can arise proceeds from the tendency in all Trematodes for the male organs to ripen before {71}the female organs. Until we certainly know that the swollen egg-bearing form (♀) does not arise from a previously male form (♂), the case is open to suspicion. Since, however, Kölliker[90] never found intermediate hermaphrodite conditions, this _Distomum_ may be almost certainly regarded as of distinct sexes. _Didymozoon thynni_ (_Monostomum bipartitum_), from cysts on the gills of the Tunny (_Thynnus_), is another case. Two slender worms flattened posteriorly, come together, and the body of one becomes folded to receive that of the other. They fuse completely except for a small lateral opening through which the anterior parts of both worms may freely protrude. The enclosing individual contains a coiled uterus filled with eggs, and is the female, whereas the smaller individual never possesses eggs, and is probably the male.[91] _Nematobothrium_ (Fig. 22, A), which occurs also in the Tunny, in the form of two immensely long individuals intricately wound about each other in a cyst, is, however, not bisexual. [Illustration: FIG. 35.—_Distomum okenii_ Köll. Showing male and female as they occur together in the branchial cavity of _Bramaraii_ (Ray's bream). (From Bronn, after Kölliker.) Nat. size.] TABLE OF DIGENETIC TREMATODES AND THEIR LIFE-HISTORIES.[92] Host into which the Host into which the larva enters, and in Cercariae migrate and Species. Final host. which Cercariae are encyst; eaten by eventually formed. final host. _Diplodiscus_ Smaller species Insect-larvae, _Rana_, (_Amphistomum_) _Rana_, _Bufo_, of _Planorbis_ _Bufo_, but frequently _subclavatus_ _Triton_ and _Cyclas_ omitted Göze _Distomum advena_ Duj. _Sorex araneus_ Not known _Limax_ (_D. migrans_ Duj.)