EQUILIBRIUM OF ANIMAL FORM^ 



BY 



HANS PRZIBRAM 



Bwlogische Versuchsanstalt, Vienna 

 With Ten Figures 



If the equilibrium of a mass be disturbed, the body will alter 

 its position in regard to the surrounding neighborhood till it 

 again gets into a position of equilibrium. If the form of an 

 animal be altered through amputation of certain parts, the 

 equilibrium of mass may or may not be altered therewith, the 

 animal either being able to maintain its position or having to 

 alter its posture for readjusting its equilibrium,. But this is not 

 all that may happen: it may restore its /orw, too, after some time, 

 thus tending toward a new equilibrium of /or//?, till it has reached 

 a new stable condition. 



This may involve three regulatory processes: Regeneration of 

 lost parts from the cut surface; reduction of existing parts in 

 contact with the cut surface; compensation at parts of the bodv 

 not touched by the amputation. 



The study of regeneration has long received much attention; 

 of late reduction too has been studied more fully, especially in 

 the lower animals, whilst compensation as a means of restoring 

 animal form seems first to have been pointed out by me. Its 

 study has been taken up especially in America, where Zeleny 

 found additional cases (observed independently of my work), 

 and Wilson, Morgan and Emmel have studied different aspects 

 of compensatory regulation in crustaceans. 



Having found the principle of compensatory regulation illus- 

 trated in the chelae of Alpheus, I have been looking for other analo- 

 gous cases and have found the same process in other crustaceans, 

 especially Callianassa and the common Crabs, Portunus and 



^ Read before the International Congress of Zoology at Boston on August 22, 1907. 

 The Journal of Experimental Zoology, vol. v, no. 2. 



