xxvi INTRODUCTION. 



this the animal remains for a considerable time in a 

 languid state, and is quite transparent and colourless." 



The new creature is a perfect representation of the old 

 one, slightly enlarged. According to our observations, 

 every hair is produced complete. We have often seen 

 them, convoluted and bent up within the old case, from 

 which they only wanted to be freed to assume the erect 

 position of the perfect hair. It has, however, contrary to 

 our anticipation, appeared that all the hairs are not de- 

 veloped within each corresponding one. We have fre- 

 quently observed them as a second armature, independent 

 of the old one. This remark is particularly distinguish- 

 able in the teeth that fringe the first two siagnopoda. 

 These have generally a dentated arid forked character, 

 which might be injured in their removal from the old and 

 hard tissue of the rejected skin, an accident that not 

 unfrequently befalls the branchial sacs, which are occa- 

 sionally torn off and retained behind in the old case. 



The power of Crustacea to throw off any of the limbs 

 upon receiving an injury, and sometimes in consequence 

 of fright, is well known in relation to the higher orders. 

 The manner in which this is done has been described by 

 Dalyell, Goodsir, and ourselves. It certainly is a remark- 

 able power and law of reproduction, and which always 

 takes place at the same homotypical position in every 

 limb that is, between the coxa and the next succeeding 

 joint. The wound that is caused by this sudden rupture 

 is simultaneously glazed over by a thin membrane, which 

 must be very suddenly formed, and probably is the ampu- 

 tating power. Observers have very generally added as an 

 appendage to- the above interesting fact, that it is exceed- 

 ingly fortunate that there is this power of voluntary 

 amputation of the limbs, for otherwise, in consequence of 

 the non-contractile character of the dermal covering, the 



