Control of A svuiiiu'fry 481 



that this inverse organization may be due to the maturation of the 

 egg at opposite poles in dextral and sinistral forms ('05, p. 10). 

 On this basis, the alternate appearance of right or left asymmetry 

 in the lobster might be regarded as cases of inverse symmetry 

 "resulting from slight alterations in the localization of germinal 

 substances in the unsegmented egg." 



Morgan ('07) does not venture to decide between the possibili- 

 ties of "inheritance" and the structure of the egg, as determining 

 right or left handedness in various species. He says "both possi- 

 bilities seem to exist in the egg; but whether this can be referred to 

 alternate dominance and recession, or to purely local conditions 

 that arise during segmentation, is unknown" (p, 165). 



It is evident that the present experiments at least demonstrate 

 that the asymmetry of the adult lobster is not necessarily inherited 

 nor even predetermined in the egg. However, the question still 

 remains as to what factors in normal development determine 

 right or left asymmetry. No evidence was found that the occur- 

 rence of right or left asymmetry in the lobster can be referred to 

 germinal units having "alternating dominance and recession." 

 The fact that in early development a crusher can be produced on 

 either side of the body by the amputation of the opposite chela, 

 indicates that the factors which control asymmetry become opera- 

 tive after hatching. What these factors are, or how they may be 

 released by the amputation of a limb, is not known. We can 

 merely refer to the fact that in early stages of development of the 

 lobsterthe asymmetry of the chelae can be experimentally controlled. 

 When asymmetry has once been normally established, similar 

 experiments no longer reverse it. 



That the accidental loss of a limb in the young lobster may 

 play an important role in determining the asymmetry of the adult 

 is not improbable. For the autotomy of a chela during the exigen- 

 cies of moulting or as the result of injury, is a common occurrence, 

 especially among young lobsters. In an examination of several 

 thousands of fourth stage lobsters it was found that a large per 

 cent of the animals had lost either the right or left chela. In these 

 the right or left asymmetry would not be inherited or due to the 

 structure of the egg. 



