NATURAL HISTORY OP AMERICAN LOBSTER. 285 



the regeneration of the new limb. To summarize briefly her account, the process of 

 actual regeneration begins in about 5 days after the loss of the original member by an 

 extension of ectoderm over the opening, which thus replaces the blood plug formed at 

 the time of injury. Later these same cells secrete chitin and form a thickened disk over 

 the broken end of the nerve. The ectoderm pushes out into a growing, expanding tip; 

 its cells become elongated, join the cells of the old nerve, and reconstruct those of the 

 new one. As the bud grows out, muscles and nerve are regenerated from ectoderm 

 cells and folds in this layer appear, thus marking out the future podomeres of the new 

 limb. The folds, which arise as ingrowths of ectoderm, also secrete chitin; they split 

 to form the folds of the joints and, finally, at their ingrowing ends give rise to the tendons 

 of the muscles and to the muscle fibers which are attached to them. 



Emmel (97) has obtained similar results in working upon the lobster, wherein the 

 wound caused by autotomy is soon covered by a plate of migrating epidermic cells. 

 The wall of the limb and possibly its core were found to be epidermic, the old muscle 

 and connective tissue cells of the stump appearing to contribute little to the new append- 

 age. Both new nerve and new connective tissue elements seemed to owe their origin 

 to the epiblast of the regenerative bud. 



MONSTROSITIES. 



The curious monstrosities that occur in the appendages, particularly in the large 

 claws of the lobster, have attracted the attention of naturalists from early times. They 

 were noticed by Von Berniz over 200 years ago, and some good figures of the deformed 

 claws of the crayfish were published by Rosel in 1755.° Among the later students of 

 variation Bateson (79) has shown that in most of the cases of supposed duplication of 

 Umbs in both insects and crustaceans the extra parts are double instead of single, as where 

 two dactyls are formed at the extremity of the claw instead of a complete claw consisting 

 of dactyl and propodus. He has also formulated certain principles according to which 

 supernumerary appendages make their appearance in secondary symmetry. If the 

 normal appendage which bears the extra ones is a right leg, "the nearer of the extra 

 legs is a left and the remoter a right." 



The monstrosities noticed in the chelipeds of the lobster are mainly the result 

 of a secondary outgrowth from one^pf the two terminal segments. Rarely the appendage 

 is duplicated or triplicated. In some cases the extra appendages are perfectly formed, 

 while in others deformation has been carried to excess, resulting in irregular branching 

 processes or grotesque contortions. Injuries to the claws are excessively common, 

 while duplication of the parts is rare. Defective or deformed claws, the result of 

 injuries in different stages of repair, are met with every day by dealers, while thousands 

 of lobsters may be examined without meeting a single case of repetition or duplication 

 of parts. 



If the tips of the claws are snipped off near the articulation of the dactyl, the lost 

 parts are restored at the next molt without autotomy taking place. This is called 

 simple regeneration by Przibram {221). This restoration is often perfect, but not 



Jlnsecten-Belustigung, dritter Theil. Nuernberg, lyss- 



