166 STUDIES IN GENERAL PHYSIOLOGY 



tube, the former constructs a firm tube of mucus in the 

 course of a few hours, while the latter which is kept in a 

 test-tube, and the skin of which encounters but little friction 

 from the smooth glass, forms a scarcely perceptible veil in 

 the course of twenty-four hours. The greater amount of 

 friction brings about a greater secretion and a more exten- 

 sive tube -building. 



3. I fastened a Cerianthus to the underside of a cork 

 floating at the surface of the aquarium. The Cerianthus 

 was fastened to the cork by passing a pin through its body. 

 The head and foot of the animal hung down loosely upon 

 either side of the pin. I waited four weeks, but no mem- 

 brane was formed upon the parts which did not come in con- 

 tact with solid bodies. But a secretion occurred at those 

 places where the Cerianthus rubbed against the cork or the 

 head of the pin. The mass .of mucus secreted at these points 

 attained the thickness of a finger in four weeks. 



The wound occasioned by the pin was not the cause of 

 this secretion, but only the friction, for I observed the same 

 phenomena in uninjured Cerianthi which remained for some 

 time in the meshes of a wire screen. Only in the latter case 

 it is very difficult to keep a Cerianthus very long in this 

 position without movement. 



The formation of a tube by Cerianthus offers therefore 

 the same evidence of "artistic impulse" as the secretion of 

 saliva during mastication. 



XV. EXPERIMENTS ON ORGANIZATION AND IRRITABILITY IN 

 SOME OTHER ACTINIA 



1. I have made experiments similar to those upon Ceri- 

 anthus on the determination of the situation of the new head 

 in a number of other Actinians Actinia equina of the Bay 

 of Naples and the East Sea, Actinia cari, Adamsia Rondel- 

 letti, Anemonia sulcata, Cereactis aurantiaca, etc. 



