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The embryonic development of the leech Batracobdella algira (Monquin-Tandon, 1846) was studied for the first time under laboratory conditions. The studied leech is semelparous, reproducing once and then dies few weeks later. It has a hypodermic mode of insemination. In fact, observations of histological sagittal serial sections have shown a sperm mass in the parenchyma of the recipient animal. Five main stages of development were distinguished by means of dissecting microscope and optical microscopy. The specific patterns of egg plates, the numbers of embryos per cocoon, and the major stages of the embryonic development were documented. The duration of embryonic development is between 20 and 22 days at 18 °C in laboratory condition.