The spawn and embryonic development of two colour morphs of the aeolid nudibranch Facelinella quadrilineata (Baba, 1930)

Two colour morphs of Facelinella quadrilineata spawned slightly different egg masses and the eggs enclosed were also different in colour and size. The time required for embryonic development of larger ova was always longer than that of smaller ones. Both of them hatched as lecithotrophic veliger larvae with relatively small vela, welldeveloped large eyespots and propodium, although the shell shape and size were fundamentally different between the two morphs. These findings, together with sympatric and simultaneous occurrence, strongly suggest that the two colour morphs represent two distinct species.