218 FOUNDERS OF OCEANOGRAPHY 



EcHiNODERMATA. — Comparatively few of these are known 

 to produce light. Some Ophiuroids (" Brittle-stars "), 

 however, show a brilhant luminescence, which in the case of 

 Ophiacantha spinulosa is said to be of a uranium green colour. 

 Wyville Thomson, describing some specimens dredged 

 from deep water south-west of Ireland, writes : " The 

 light from Ophiacantha spinulosa was of a brilliant green, 

 corruscating from the centre of the disc, now along one 

 arm, now along another, and sometimes vividly illuminating 

 the whole outHne of the starfish." In this and a few other 

 Ophiuroids the light has been shown by recent investigations 

 to come from internal cells in the tissues of the ventral and 

 lateral plates and spines of the arms. 



Vermes. — Many of the higher worms; or Annelids, are 

 luminescent. In the Polynoids the light is emitted from 

 definite light-organs arranged round the posterior edge of 

 the elytra or scales which cover the dorsal surface of the 

 worm, and as the eljrtra continue to glow with a bright 

 light for some time after being detached from the body, 

 this seems to be a case where the use to the animal of its 

 luminescence is to distract the attention of the fish, crab, 

 or other enemy. 



In some of the Syllid worms the light -production is 

 definitely related to reproduction, and is apparently of use 

 in enabling the male to find the female on the surface of 

 the sea during the periodic swarming for the purpose of 

 mating. The light is produced from very definite Hght-glands 

 placed in lateral series at the bases of the parapodia. 



The light from some of these Annelids is described as 

 violet blue, and in other cases as greenish blue. I have 

 frequently seen a most vivid green light produced by a 

 small polychaet worm which we dig up from the sand or 

 from the debris round the roots of Laminaria at Port Erin. 

 The light is even visible for a few seconds in the sunlight. 



But the most brilUantly luminescent of all marine worms 

 is certainly the tube-building Chcetopterus, which was studied 



