In the present study, the larval development stages in the egg capsule of the Japanese snail (Rapana thomasiana, Gross 1861), distributed in the Black Sea were investigated. At the moment of capsule release, the diameter of the spherical egg was 151.5 ± 2.61 μm. After the capsule was released, the eggs gradually lost their spherical structure. After the completion of the early larval development stage in the egg capsule, the larvae hatched from the capsule as a veliger on day 20. The larvae were pelagic during the following 5 days and settled to the bottom day 25. The length and width of the settled larvae reached 426.8 ± 2.84 μm and 305.6 ± 2.2 μm with a growth rate of 181.2% and 101.7%, respectively.