gth December, igij. 



Mr. H. Riddell, M.E., in the Chair. 



THE NATURAL HISTORY OF FLATWORMS. 



By Mr. Richard H. Whitehouse, M.Sc. 



{Abstract) 



The Chairman briefly introduced the lecturers, and expressed 

 the hope that Professor Lindsay would shortly enjoy his customary 

 good health. 



The Lecturer in the course of his paper dealt with 

 the various classes of flatworms, and, proceeding, said that the 

 characteristic mode of movement among planarians was by means 

 of short and indefinitely numerous hairlike structures, which 

 covered the body like a fur, but so minute and transparent as to 

 be invisible to the unaided eye. Such structures were called cilia. 

 The planarian did not come into actual contact with the surface 

 over which it glided, but laid down a mucus, just as a snail did, 

 and it was on the smooth surface of its own mucus or slime that 

 it moved. The slime was produced by glands distributed all over 

 the lower surface, particularly at the edges. An interesting des- 

 cription was given of the " testing movements " of the planarian, 

 and the lecturer, continuing; said the important thing to grasp was 

 that a planarian would move towards all weak stimuli and test 

 them. In truth the planarian "proves all things, holding fast only 

 to that which is good." Past experience had an important bearing 

 on an animal's attitude towards things around it. Probably the 

 most interesting and instructive studies in animal behaviour, based 

 on experience, which had been brought to light within recent 

 years, were those on convoluta. Convoluta roscoffensis was a 

 slowly organised flatworm which lived on the sandy shores of 

 Brittany, between the tide rnarks, in such large numbers as to forni 



