16 



PLANT-ANIMALS 



[CH. 



savour of exaggeration, it may be said that one colony 

 of moderate size extending over some two square 

 yards was found by estimation to contain 5,600 

 million individuals. Of such flaky thinness are these 

 animals that as many as 28,000 may be packed in a 



n. 



Fig. 6. Kesponse of C. roscoffensis to vibration. Eeproductions of 

 photographs of a colony. I. before, II. five minutes after the 

 sand had been tapped lightly with the foot. The dark patches 

 in I. represent vast numbers of the animals which in II. have 

 disappeared almost entirely below the surface of the sand. 



space measuring one cubic centimetre. A search on 

 dark nights at low tide in the roscoffensis zone fails to 

 reveal any of the animals upon the surface. In such 

 circumstances they remain just beneath the sand. 

 On moonlight nights, some, but not many, may be 



