Crustacea. 755 1 



development. A small papilla becomes visible and goes on increasing 

 behind the membrane, causing it to protrude more and more as its 

 own growth increases; but the membrane never breal<s, for the new 

 limb is part of a new animal within, and has little or no connexion 

 with the old shell ; within the membrane the limb lies bent up and 

 passive until the period arrives that frees it from its position, 

 when it appears as part of the new animal, and is in size greater or 

 less, according to the length of the time that has elapsed since the 

 loss of the old limb. In this condition, either large or small, it con- 

 tinues, as the rest of the animal, stationary in growth, until the 

 next period of shedding the exuviae, when it will be found to have 

 advanced in size equal to its proportion relative to the animal. 



Naturalists have generally assumed that this power on the part of 

 these hard-skinned animals was given them in order that they might 

 have, within their own means, the capability of overcoming the dis- 

 astrous results of an injury ; for, otherwise, a limb having been lace- 

 rated or torn off the animal, enclosed as it is within a most unyielding 

 tissue, must of necessity bleed to death. 



In all the natural sciences there is nothing more likely to lead 

 to error than deductions based upon negative evidence. That 

 an animal might bleed to death under such circumstances appeared a 

 most probable hypothesis ; but investigation among the lower forms 

 proves that the Amphipods have not the power to throw off their limb 

 on the receipt of an injury ; and in the higher forms, also immediately 

 after moulting, the limb is not rejected for half an hour or more while 

 the external tissue is soft. If a leg in an Amphipod be broken off, 

 the wound appears shortly after to cicatrize over with a black scar; but, 

 so far as opportunity has enabled a judgment to be formed, the part 

 is never thrown off. A limb upon being lost is capable of being 

 reproduced, but the injured limb is not thrown off at the time that the 

 injury is received, but probably at the period when the whole of the 

 dermal tissue is exuviated ; the new limb commences at that or some 

 earlier period still, and continues its growth after the manner of the 

 preceding. 



The exhibition of indifference in these creatures to the loss of one 

 or more limbs is an argument made use of by philosophers to prove 

 that animals that have no true brain cannot suffer pain ; that the 

 writhings, like those of the worm upon the fisherman's hook, are the result 

 of a reflex action only. I am not one of those who think that we ought 

 not to inflict suffering upon the lower forms of life, if there be sufficient 

 reason for doing so. To obtain knowledge of a single undiscovered 



