THE RIGHTING REACTION IN ASTERINA GIBBOSA. 423 



27. Note on the Righting Reaction in Asterina gihhosa Penn. 

 By E. S. Russell, M.A., B.Sc, F.Z.S. 



[Received October 22, 1919 : Read November 18, 1919.] 



Introductory. — The experiments to be described in this paper 

 were carried out in June 1919 on the beach of Porthmear, a 

 Httle rocky bay in North Cornwall between Trevose Head and 

 jS'ewquay. A small colony of Asterina lived in the rock-pools 

 of this bay about halfway up the beach. They did not extend 

 further to seaward, and the reason for this appeared to be that 

 their habitat midway up the narrow land-locked cove was less 

 exposed to wave-action than the lower section of the beach, 

 which at low water ran continuous with the coastal line of cliffs. 

 The method of experimentation was simple — the starfish were 

 collected in twos and threes, generalh^ from the underside of large 

 stones, and transferred at once to shallow rock-pools, in which 

 they could be closely observed. No specimen was used for more 

 th.an ten experiments, so as to eliminate the factor of fatigue. 



I attach some importance to the fact that the observations 

 were made under natural conditions, for it is obvious that if one 

 removes animals from their natural surroundings to the artificial 

 conditions of a laboi-atory experiment their behaviour is apt to 

 be upset by the change. Few animals seem to take kindlj'^, for 

 instance, to life in a smooth glass basin exposed on all sides to 

 the light, and it is improbable that their behavioui' remains 

 miaffected by such strange surroundings. Furthermore, there is 

 always the risk of aquarium specimens losing vigour and getting 

 out of condition. Plessner (1913) says of Asterias rubens and 

 Solaster "papioosus weakened by aquai-iiim life that they right 

 themselves only with difficulty or even fail to turn. 



It is best, then, when studjdng the behaviour of any animal to 

 study it in its native haunts or in surroundings approximating as 

 nearly as possible to those natural to it. This was comparatively 

 easy to manage with the Asterinas of Porthmear, and the obser- 

 vations recorded below, scanty though they are, have at least 

 the merit of referring to animals acting normally in a noi-mal 

 environment. 



The Righthig Reaction. — Records were kept of the righting 

 reaction in eleven individuals of various sizes, the exact way in 

 which the righting movements wei'e performed being noted, as 

 well as the time taken, from the moment the starfish was placed 

 on its back to the moment when it i-ecovei'ed its normal position 

 and started to crawl away. The rapidity of the reaction in many 

 cases was striking, nearly 40 per cent, of the turnings observed 

 being completed in 20-30 seconds. These times compare favour- 

 ably with the times taken by Ophiura hrevispina, which accord- 

 ing to Glaser (1907) averages 45 seconds for the turn. On the 

 other hand, if things went wrong and the starfish got tied up in 



