Control of A symmetry 



477 



The lobsters were mutilated by the autotomous removal of the 

 right chelae July, 1907. The mutilations were made about four 

 days after the moult to the fifth stage. Through the kindness of 

 Dr. A. D. Mead and his assistant, Mr. L. N. Wight, some of the 

 lobsters were kept alive until the final data could be obtained in 

 September. The results are shown in Table III. 



TABLE III 



Lobsters in the fifth stage. Original chela symmetrical. Removed right chela 

 four days after moult to fifth stage July, IQ07 



* By September 21, these lobsters were apparently all in the seventh stage, although 

 the stage cannot be positively stated because a record of all the moults was not obtained. 



These results are in marked contrast with those obtained for 

 the preceding stages. Instead of all the uninjured claws pro- 

 ducing crushers, they produced three crushers and four nippers. 

 At the same time, the regenerated claws, instead of being all nippers 

 include three nippers and four crushers. Since in the adult lob- 

 ster the crusher appears about as frequently on one side of the 

 body as the other (and this is equally true of the nipper), it appears 

 that the normal development was not modified by the removal of 

 one chela. Evidently therefore during the fifth stage, in which 

 the chelae are apparently still symmetrical, the controlling influence 

 of such amputations upon symmetry disappears. 



