The adult worms were collected from rats 30 days after infection with metacercariae of Echinostoma hortense which cysted on the gill of Misgurunus anguillicaudatus. The testis and ovaries of matured worms were extracted from live adult worms and there were stained with 45% aceto-orcein solution for chromosome observations. The results of the study are briefly presented as follows.
1. Ten bivalent chromosomes can be seen in both primary spermatocytes and oocytes, which signifies the diploid number of chromosomes to be 20 (2n=20).
2. A spermatocyte is divided into four spertides after binary division.
3. The spermatozac after being transformed into the same number of spermatides, pass through vas deferens and wanter out to the seminal vesicle, and after copulation there, they are ejected into the uterus.
4. When the ovum has moved to the center of ovary, it reaches the leptotene stage and is inseminated.
5. The cocyte after insemination enters into egg-shell at ootype and then migranting towards the uterus, under goes two mitotis (meitotic) division and is transformed to prenucleus.
6. Sperms are gradually enlarged within the oocyte and forming the nucleus, now are transformed to sexual pronucleus. Oocytes that have formed sexual pronucleus in the center of uterus undergo karyogamy near she periphery of uterus, and after the first cleavage of ovum, there are formed two cells of a large and a small one each having 2n=20 chromosomes. Subsequently, they undergo the second cleavage to form one large cell and three small cells. At the time of spawning the ovum is composed of the primary and secondary polocytes and a cell at the fourth cleavage as well as a vitelline cell just before disintegration.