日本血吸虫病的媒介钉螺也是外睾吸虫的中间宿主。本文报告外睾吸虫早期幼虫在钉螺及窄口螺的奇特发育形式及贝类宿主的反应情况。贝类宿主吞食外睾吸虫虫卵后 1 2天 ,毛蚴体中的胚细胞已穿过宿主胃肠壁分散在其外围组织中。螺体在其头颈部产生大量血淋巴细胞并下行到内脏团包围虫体的胚细胞。生存的虫体胚细胞分散地通过宿主循环系统被送到消化腺及生殖腺的间隙中发育成早期雷蚴胚球。在雷蚴胚球周围尚有开始消退的宿主血淋巴细胞残体。这种现象在吸虫类幼虫期发育中甚为罕见 Schistosoma japonicum is also the intermediate host of the genus Schistosoma. This article reports the peculiar developmental pattern of the early larvae of Schistosoma japonicum in snails and snails and the response of shellfish hosts. After the shellfish host swallows the eggs of the epidermal testes, 12 days later, the blast cells in the miracidium have spread through the gastrointestinal wall of the host and dispersed in the peripheral tissues. Spiro in its head and neck to produce a large number of blood lymphocytes and down to the viscera surrounding the worm body embryo cells. Survival of the insect cells blastocysts dispersed through the host circulatory system is sent to the gland and gonadal gap into the early germ cell germ. Survivors in the echinococcosis there are still beginning to subside the host blood lymphocyte remnants. This phenomenon is very rare in the development of trematode larvae