260 Hans Przihram 



Carcinus, as I demonstrated at the last session of the German 

 NaturaHsts' Association. It will be remembered that this com- 

 pensatory regulation consists in the hypertypical growth of the 

 smaller claw of the first pair of thoracic limbs, after autotomic 

 removal of the bfg chela, whilst a hypotypical small chela regener- 

 ates. That such a "transposition" or "reversal" need not be 

 restricted to this pair of appendages I am now able to show in 

 Typton spongicola (Fig. i), where the second pair of thoracic 

 limbs is developed into asymmetrical chelae. After removal of 

 the bigger chela, which, by the way, maybe situated normally at 

 the right or at the left side of the body, reversal of the chelae of 

 this second pair is brought about (Fig. 2), the process being in 

 all respects analogous to that in the first pair of chelae in Alpheus. 



But not only may the means of regeneration and compensation 

 be clearly shown to occur in this case, but also reduction is 

 involved to an appreciable degree, especially if the crayfish is 

 starved during the experiment. Then each moult shows the 

 shedding of a smaller skin and the animal is at the end of the 

 transposition in all dimensions smaller than at the time of the 

 operation. Thus, as in the lowest animals, a proportionate 

 diminution of the whole form may be produced as regulation 

 proceeds, the only difference with Morgan's ''morphallaxis" lying 

 in the bigger fragment necessary for reconstruction. 



A curious instance of "compensatory reduction" was met in 

 some experiments on cutting the nerves in crabs. As Morgan 

 has reported, the chela generally degenerates after this operation. 

 In a few cases, however, I was fortunate enough to get a further 

 growth of the hmb. In these the terminal joint of the big or 

 crushing claw was removed (Fig. 3), and in one instance regenerated 

 in a rather reduced state; but also the corresponding dactylopodite 

 of the smaller or nipping claw lost its differentiation (Fig. 4). 



Compensatory reduction may also occur in animals other than 

 crustaceans and in other regions than in the chelae. Megusar, 

 working on regeneration in beetles (Coleoptera), amputated one 

 of the two slightly differing jaws of the Hydrophilus larva. Whilst 

 there are normally two teeth on the inner side of each jaw (Fig. 5) 

 the larva appeared after the moult succeeding the amputation 



