1905-1906.] Report of the Microscopical Section. 317 



are " trichocysts " in Paramoecium — very small, special, cilia- 

 like organs for defence ; and " nematocysts " much larger in 

 Vorticella and others. These act like the thread - cells in 

 coelentera. Another specialisation is the muscular fibrils 

 (myonemes) in, for example, the stalk of the Vorticella. 

 Then the simple cell can secrete, say, chitin or cellulose, or 

 carbonate of lime in most beautiful forms, as in foraminifera ; 

 or silica may be deposited in a network of hexagonal meshes, 

 and from these prolongations in most artistic shapes may 

 arise. It may be recollected that the architect of the late 

 great exhibition at Paris frequently visited the Mus^e 

 d'Histoire Naturelle to study the models of radiolarians, 

 and from these he got ideas for the great entrance. 



I have made these remarks to show how many things a 

 single cell can do. One of the most interesting investigations 

 that have been made lately is studies about what may almost 

 be called the mental qualities of the Protozoa, by an American, 

 Jennings, and others. It may be remembered that Haeckel 

 said that every particle of matter-stuff had a particle of mind- 

 stuff associated with it, or something to that effect. It may 

 be crudely expressed, but it represents a great solid fact. 

 Verworn and Laeb, ten years or less ago, propounded the 

 theory of " tropisms," which has had a great many followers, 

 and was an attempt to explain the movements of these 

 organisms — say paramoecia, and many others. Explained 

 briefly, stimulus excites or retards the movement of cilia 

 on which it falls, and so the organism is steered about 

 automatically. According to Jennings, that is not enough 

 to account for the phenomena. Lloyd Morgan (' Introd. to 

 Compar. Psychol.,' p. 257) tells of a dog which he wanted to 

 bring a hooked walking-stick through a narrow gap in a fence. 

 The dog seized the stick anywhere about the middle and tried 

 to carry it through the gap. He could not get it through in 

 that way, and dropped it. Again and again he seized it 

 much in the same way, with the same result. At length 

 he caught hold of it by the hooked end, and got it through 

 easily. • This is called by Lloyd Morgan the method of trial 

 and error; and Jennings concludes from his experiments that 

 paramoecia and other free-swimming, single-celled organisms 

 act in the same way. He writes a report of over 200 pages, 



