350 LUMINOUS ORGANISMS OF FAR EAST 



Among Pelecypoda, Pholas dactylus was at one time thought to be 

 the only luminous species. However, in 1939 at Palao, I found that 

 Rocellaria grandis, a coral boring shell, is also luminous. This animal 

 has a thin white shell 45 mm long, 15 mm wide, and 15 mm in height. 

 I have collected living Rocellaria from the living corals Favites virens, 

 Goniastrea parvistella, and Pontes tenuis in Iwayama Bay of Corror 

 Island, Palao. Rocellaria has a pair of luminous stripes on the mantle 

 along the pallial lines and produces a luminous secretion which fills 

 the mantle cavity and spouts from the siphon when irritated. The 

 dried luminous tissue recovers its luminosity when moistened and the 

 luciferin-luciferase reaction is positive. 



Among the Gastropoda Pulmonata it was thought that Latia neri- 

 toides (Suter, 1890), a New Zealand fresh water limpet, was the only 

 luminous species. It has been fully studied by Bowden (1950). How- 

 ever, we found a luminous snail, Diakia striata of the Zonitidae, in 

 Singapore. One night in September, 1943, when Mr. Kumazawa, 

 entomologist, was collecting luminous larvae of fireflies on the lawn 

 of the Good Wood Park Hotel, Scot Road, Singapore, he saw a weak 

 Hght from a small land snail and informed me of the possibility of 

 luminescence in land snails. The next evening we went to the place 

 and were astonished to observe a true luminescence in this animal. 



The snail, about 10 to 15 mm in diameter, lives on grass or lawns 

 in Singapore. The type specimen in Raffles Museum was collected 

 from Gunung Pelai, Johore. I have also collected specimens in various 

 regions of the Malay Peninsula and Kalimon Island of the Rhio 

 Archipelago. The light appears inside the anterior region of the foot 

 and cannot be seen when the animal is irritated and has withdrawn 

 within its shell. When expanded the bluish white light passes through 

 the translucent muscles of the head and of the foot and flickers like 

 a firefly. The time relations of the flashing depend on the stage of 

 development of the snail and various other conditions, such as tem- 

 perature, humidity, and light. Young snails, immediately after hatch- 

 ing, about 1 mm in shell diameter, emit a weak luminescence over 

 the entire foot. The light appears continuous, but on close inspection 

 the diflFused glow can be resolved into small flashes scattered over the 

 area. As the snail grows, the flicker rate diminishes, and some full 

 grown individuals do not luminesce at all. The normal duration of a 



