217 



from the tìrst, -i. e. it seems to be more easy to reinduce the persistence 

 of a particular impression that it was to induce it originally. 



V. When a number of anemones of various species are kept in 

 aquaria subject to fairly marked variations of illumination, it will be 

 found that, on the whole, more individuals will be open when the light 

 is weak or absent, though the common Actinia does not show any re- 

 action as far as we can tell. Gosse mentions that Phellia brodricii 

 closes if a light is brought near. Nagel (1894) finds that Cerianthus 

 closes when illuminated but neither Adamsia nor Antliea do so. One of 

 us hunted several pools at a spot on the N. Wales coast without suc- 

 ceeding for some time in finding any anemones. The pools were shallow 

 and open, but contained a few inches of mud at the bottom. As it 

 grew dusk, however, several individuals of Sargartia bellis pushed up 

 through the mud and expanded their black and white tentacular crowns 

 above its surface. 



Tealia crassicornis is by far the most interesting species in this 

 connection. It lives in the moist chinks between rocks and under boul- 

 ders, well below half-tide level, so it is under Avater for perhaps 8 hours 

 each tide or even more. The exact conditions of its life vary conside- 

 rably with the spot selected and this is the case more especially with 

 regard to the average illumination it receives. Many individuals of 

 Tecdia will remain closed during the day, or at any rate whilst they are 

 exposed to fairly bright light, but their reactions differ according to the 

 situations in which they have lived previously. Those which had lived 

 in rather well illuminated situations, for example, showed less aversion 

 to bright light, and gave sometimes no regular reaction when artificial 

 light was thrown on to them in the expanded condition at night. Those 

 which had lived fairly deep in the shadow usually, though not always, 

 closed when artificial light was thrown on the expanded tentacles at 

 night ; the reaction is slow, but closure is nearly or quite complete after 

 about five minutes exposure. 



This sensitiveness varies from one individual to another and in the 

 same individual according to its condition at different times, but, on the 

 whole, those with white tentacles are most sensitive, those variegated 

 red and white less so, and the dark red ones least of all. Occasionally 

 the anemone reopens after closing as just described. 



It is possible that these reactions to the stimulus of light may have 

 biological value in various directions. Many kinds of prey will be more 

 likely to stumble on the anemones when it is dark than when their 

 powers of sight help them to avoid the danger, and anemones in sunny 

 pools might suffer detriment from high midday temperatures if they 

 remained open too long. W^e may mention that Actirtia and Anthea 



15 



