113 Papers from the Marine Biological Laboratory at Tortugas. 



satisfactor}', because of the few cases on which they are based and because 

 of the lack of quantitative data. 



In Portunus sayi it has been found that the amount of regeneration of 

 the right chela increases regularly with the size of the animal between the 

 limits of 3 and 15 mm. This increase is slightly greater than the increase in 

 size, so that large individuals have a greater specific amount of regeneration 

 than small ones. This increase in specific amount of regeneration is simi- 

 lar to the increase in specific length of the chela with size in unoperated 

 individuals. Thus the chela regenerates at a rate which is proportional to 

 the size of the removed chela, and when the regenerated chela-length is 

 divided by the removed chela-length a quotient is obtained which is fairly 

 constant for all sizes of individuals. 



The effect of successive injury upon the regeneration of the right chela. — 

 The efifect of successive removal upon regeneration is mentioned again and 

 again in the literature, but almost always in an indefinite way. According 

 to the usual statement, a part capable of regeneration may be removed many 

 times in succession without afifecting its power of regeneration. The ob- 

 served facts upon which this statement is based are as indefinite as the state- 

 ment itself. The only definite contrary data I have been able to find are 

 referred to in Stewart's Physiology, where the statement is incidentally 

 made in describing an experiment on the regeneration of the sciatic nerve 

 in the dog that the second regeneration was more rapid than the first. 



The experiments on the gulf-weed crab {Portunus sayi) were made 

 with the object of getting definite quantitative data regarding the relation 

 between successive removal and regeneration. This form was chosen be- 

 cause it is desirable to use an appendage with a definite breaking joint, 

 insuring the absolute indentity of the plane of removal in every case. It 

 is evident that a slight difference in the plane of the cut may have a great 

 influence upon the regeneration. The Crustacea, however, have a very 

 obvious disadvantage. This is the molting habit. The regenerating chela 

 in Portunus is coiled up within a chitinous sac until the time of molting. 

 Another disadvantage connected with the same habit is the fact that the 

 comparative character of regeneration at different times during the molting 

 period has not been satisfactorily worked out. As stated above, this dis- 

 advantage has been eliminated as far as possible by making all operations 

 at the same time with relation to the molt, namely, on the day after the molt, 

 and by using the molting period and not the day as a unit of regeneration 

 time. The latter was made possible by the determination of the fact that the 

 length of the molting period influences the amount of regeneration only to 

 a very slight degree within the limits of the experiment. 



It was found that the amount of regeneration increases with successive 

 removal. An investigation of the relation of this increase to the increase 



