Tremiorchis ranarum nov.gen., nov.sp., was first found in the small intestine and duodenum of thirty-six out of one hundred and two specimens of Rana tigrina examined for the purpose. Subsequently many more frogs have been examined and we have obtained these parasites in one out of every three frogs. Rana tigrina being the commonest species of frog available in Northern India is used as the type for dissection in every laboratory and it appears, therefore, strange that this common Trematode parasite should have remained unknown till now. The number of parasites in a host is very variable. Three hosts were found infected with one parasite each, one had 4, one had 5, one 16, one 18, one 196 and one as many as 204.

SummaryOwing to the deposition of resin, the females assume two shapes, one somewhat circular in which the mouth-parts are situated ventrally about the middle of the body, and the other pyriform, in which the mouth-parts are situated at the extreme anterior end. In the former type of females the mouth-parts are posteriorly directed and in the latter anteriorly. The rostrum lies outside the body cavity between the anterior pair of oral lobes. The rostralis opens into the pharynx which lies in the tentorium. The oesophagus is elongated and passes into the colo-rectum to be succeeded by the convoluted ventriculus. The ventriculus on leaving the colo-rectum leads into the intestine, which is marked into the mid and hind intestine by the junction of the ampulla of the Malpighian tubes. The intestine after forming a loop round the greater part of the colo-rectum re-enters it close to the point of its commencement from it and continues closely attached to the outer side of the ventriculus from its distal to its proximal end; after this it comes out of the colo-rectum and runs alongside it to open into it near the anterior third of its length. The convolutions inside the colo-rectum are comprised of the ventriculus and the part of the hind intestine running outer to it. The “colon caecum” is absent. The colo-rectum opens at the anus situated at the posterior end of the insect and is divided into colon and rectum by the opening of the intestine into it.The salivary glands consist of two branches of ovoid and spherical bodies. The common duct of the salivary gland of each side runs close to the ventral ganglion and joins the opposite duct to form the terminal duct near its anterior end, which then opens into the pharynx.The nervous system consists of a bilobed cerebral ganglion which lies anteriorly to the mouth-parts in females in which the tentorium is directed posteriorly, and either laterally or ventrally to it in females in which the tentorium is directed anteriorly and lies at the extreme anterior end. The cerebral ganglion is joined by a pair of connectives to the ventral ganglion, which lies dorsal to the tentorium in females in which it is directed posteriorly, and posterior to the tentorium in which it is directed anteriorly and lies at the extreme anterior end. The ventral ganglion is followed by the nerve chord, which varies in length in either type of female. The main nerves arising from the central nervous system are described.

The author desires to express his sincerest thanks to the authorities of the Zoological and Geological Survey of India and of the Asiatic Society of Bengal for allowing him to consult the necessary literature in their respective libraries, and to the members of the Lac Association Committee and Mrs. D. Norris, the Director of the Institute, for their generous help. He is also much indebted to Mr. W. B. R. Laidlaw, the Entomologist, for going through the manuscript, and to the artist, Mr. E. Heber, for the illustrations accompanying the paper.

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