226 G. H. PARKER 



as a whole is very weak. As Pieron ('06 a, p. 164) remarked, 

 most parts of an actinian possess unusual autonomy. Or, to 

 state the matter for the whole animal as von Uexkiill ('09, p. 

 77) has phrased it for the nervous system, the sea-anemone par- 

 takes more of the nature of a sum of parts than of a unit. The 

 harmony of action that is encountered on most sides in actinian 

 behavior is in reality indicative of very little of that kind of 

 unity that pervades the individual higher animal. To speak of 

 sea-anemones as having a psychology is to use this term in its 

 very broadest sense (Pieron, '06 a, p. 169). 



5. SUMMARY 



1. The appropriation of food in Metridium involves the mu- 

 cous glands, the cilia, and the neuromuscular mechanism of the 

 tentacles, as well as the esophageal cilia and the transverse mesen- 

 teric muscles. 



2. Of these parts the neuromuscular apparatus of the tentacles 

 is the only one the activity of which bears on the question of the 

 action of the animal as a whole, and the changes which this 

 mechanism shows are in all cases referable to sensory fatigue. 

 Feeding therefore is not a unified activity, but is carried out 

 by a concourse of semi-independent parts. 



3. Retraction is produced by strong illumination and high 

 temperature. Expansion by the presence of food and by water 

 currents. Normal fluctuations in the amount of oxygen seems 

 to have no direct effect on retraction and expansion. 



4. Sagartia luciae exhibits in its retraction and expansion a 

 well marked tidal rhythm; Metridium marginatum a well marked 

 nychthemeral rhythm. Neither rhythm exhibited an anticipa- 

 tory reaction and neither persisted after the removal of its 

 rhythmic stimulus. 



5. Actinians exhibit only a low degree of organic unity which 

 is shown at its highest in their locomotion. They are organic- 

 ally more nearly a sum of parts than a unit. 



