300 Mr. C. Speuce Bate's Notes on Crustacea. 



being excited by fear are much more active and less easily caught 

 than at any other period. 



On the Reproduction of Limbs. 



VII. When a limb is injured, all Crustacea have the power of 

 rejecting it, except the wound be below the last joint * ; this is 

 done by an apparently violent muscular contraction, finishing with 

 a blow from another limb or against some foreign body : the am- 

 putation is the work of a few seconds, except when they have but 

 recently cast the exuviae, when, during the first few days (before 

 the new skeleton is hardened), they have not that easy capability, 

 and the wounded limb will sometimes remain for perhaps half an 

 hour or longer before it is rejected. 



The new limb is formed within the old shell, and lies folded up 

 until the exuviee are shed, when it appears as a part of the new 

 skeleton, the sac-like membrane which protected it being cast with 

 the annual moult, and is larger or smaller in accordance with 

 the length of time which may exist between the period of the am- 

 putation of the limb and the shedding of the skin. The condition 

 in which the limb is then, remains, as the rest of the animal, 

 stationary in growth, until the next period of shedding the ex- 

 uviae, when the whole creature again advances in size, but the 

 new limb more rapidly than the remainder of the animal, until 

 it equals it in relative proportion. 



It is therefore dependent upon the length of time which occurs 

 between the accident and the next succeeding moult, to allow the 

 new limb to develope itself, that the variety of size depends, which 

 has given rise to the prevailing idea of the limb itself continuing 

 to enlarge constantly. 



EXPLANATION OF PLATE X. 



Fig. 1. Nucleated cells from pulp of the new shell of Cancer Pagurus. 



Fig. 2. Areolar tissue from same. 



Fig. 3. Layer of pigment interspersed with small calcareous secreting cells 



and a few larger. 

 Fig. 4. New shell, the exuviae being just shed. 

 Fig. 5. Section of the slieU of Cancer Pagurus. 

 Fig. 6. Ditto of Trilobite. 

 Fig. 7. Diagram of the pulp as to structure. 

 Fig. 8. Ditto as to form : A, shell ; B, pulp of new shell ; C C, branchial 



chambers; D, stomach; F, heart. 

 Fig. 9. Leg from second pan of Pagurus Bernhardus, showing its folded 



position before the exuviae are shed. 



* I once cut the hand of a crab through the joint so as to remove only 

 the thumb and finger. The limb was not rejected, and when the shell 

 was cast, the hand continued maimed, and never was reproduced. 



