NATURAL HISTORY OF AMERICAN I.OBSTER. 275 



Out of a total of 165 larvae all but 8 were left-handed and 4 of these last are known 

 to have had a left-handed mother. Four "families" in which every one of the 130 

 members were left-handed are known in two cases at least to have had left-handed 

 mothers, the position of the crushing claw not having been observed in the others. 

 Where the children of the same family vary in this character, it is probable that the 

 parents or grandparents varied also. However, as I pointed out in 1892, the position 

 of the toothed or crushing claw is not haphazard in its primary condition, but is pre- 

 determined in the egg. 



In the next section, however, we shall see that in Alpheus as well as in other genera 

 a remarkable reversal of the position of the big claw may take place, as a result of loss, 

 so that in the course of life the crusher may shift back and forth, being now on the 

 right and now on the left side of the body. The question therefore arises whether the 

 left-handed female (no. 7 of the table), whose 44 children were all left-handed, was 

 herself left-handed at birth, and secondly, whether, as in the right-handed Alpheus 

 (no. 5), two-thirds of whose young were right-handed and the other third left-handed, 

 the shifting of the big hammer claw would influence the inheritance of the children. 

 These questions can not be answered, but it is suggested that in Homarus as in Alpheus, 

 where no loss of limbs or other serious disturbance to the processes of growth have 

 occurred, the right or left handed condition is due to inheritance. 



Emmel has recently shown that up to the fourth molt the large crusher claw may 

 be made to develop upon either side of the body at the will of the experimenter by the 

 amputation of one claw, thereby, as it were, throwing the greater quantity of energy 

 into the other for the purposes of growth. This power of control, however, ceases 

 during the fifth stage, as at all later periods when asymmetry has become established 

 and when the amputation of either chela does not normally reverse the conditions 

 present. Emmel concludes that the factors which control asymmetry are correlated 

 with the conditions of growth from the time of hatching up to the fifth stage. His experi- 

 ments show that the asymmetry of the big claws of any given animal is not necessarily 

 due to inheritance, but it would appear that in the normal course of development 

 heredity played a part, although its initial course may be subsequently changed. 



SYMMETRY IN THE BIG CLAWS. 



In 1895 {,149, p. 143 and pi. 14) I described and figured a variation in the adult 

 American lobster in which both big claws were similar and of the toothed type. This 

 variation was exceedingly rare, as shown by table 7. Only three cases of this abnormal 

 symmetry were found in this collection of 2,433 lobsters made in the Woods Hole 

 region by Mr. Vinal L. Edwards, the veteran naturalist and collector of the United 

 States Fisheries Laboratory. 



Since that time several papers have appeared upon this subject by Stahr {258), 

 Przibram {220), Caiman {45), Emmel (pr, 92, and 93-96), and myself." The first of 



o The account whicli follows is partly taken from an article on ' Symmetry in big claws of the lobster " (no. 155 of bibliography) . 

 62399°— 11^— 9 



