1()G 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 011 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, Anemoiiia sulcata, Cereactis auraiitiaca, etc. 



