52 report — 1877. 



tare of this glandular-liko body is very peculiar, consisting of a great number 

 of large nucleated cells, which are interspersed throughout a fibro-gelatinous 

 mass. A single branch of each of the great vessels, accompanied by a branch 

 of nerve, runs through a small foramen near the centre of this body, but 

 there is no vestige of either muscle or tendon, the attachments of which are 

 at each extremity. In fact this body is perfectly denned, and can 

 be turned out of the shell without being much injured. When 

 the limb is thrown off, the blood-vessels and nerve retract, thus 

 leaving a small cavity in the new-made surface. It is from this cavity that 

 the germ of the fixture leg springs, and is at first seen as a nucleated cell. 

 A cicatrix forms over the raw surface caused by the separation, which after- 

 wards forms a sheath for the young leg." 



When a part receives a hurt beyond repair, or sometimes for a 

 less cause, such as a passing fright received by the animal or from 

 the dread of capture by an enemy, a crab or lobster will throw off 

 the injured limb. This 'appears to be known to them, for it not unfre- 

 quently forms a plan of attack on one another. I have known the common 

 Velvet-Crab (Carcinus puber) attack for some purpose the common Shore- Crab 

 (Carcinus mcenas), and, with a pinch from its nippers, induce the weaker 

 animal to eject all its legs in rotation, and leave it a helpless mass, at the 

 mercy of any passing terror. But when a limb receives a less intended 

 injury, it appears to be removed by a violent muscular contraction, termi- 

 nating with a blow given by another limb or against some foreign body. 

 The amputation is the work of a few seconds, except when the exuvia has 

 been recently cast ; then for the few succeeding days before the external 

 shell is hardened it has not that easy capability, and the wounded limb 

 will sometimes remain attached to the animal for half an hour or longer 

 before it is rejected. (Ann. Nat. Hist. 1851, vol. vii. p. 300, "Notes on 

 Crustacea.") 



The newiy-formed limb is developed within the old shell, and lies folded 

 within its case until the animal moults, when it appears as part of the newly 

 perfected animal, the sac-like membrane in which it was folded being cast 

 with the rest of the exuviae. The new limb is larger or smaller in accord- 

 ance with the duration of time which elapsed between the period that the 

 limb was amputated and that at which the skin is shed. The form and con- 

 dition iu which the limb then is in remain to all appearance stationary 

 until the next time of moulting, when the whole creature again advances in 

 size, but the new or small limb more in proportion than the rest of the 

 animal, until it equals it in relative proportion. 



The size of the restored appendage is therefore dependent upon the length 

 of time which occurs between the accident and the next succeeding moult — 

 that is, the length of time from the commencement of repair to that when 

 the limb is freed from the saccular membrane. 



The legs during development generally lie folded upon themselves ; but the 

 long flagelliform appendage of the antennae is adapted to a spiral case until 

 ihe period of the general moidt arrives, when it is withdrawn, and assumes a 

 straight lino, the old skin retaining its spiral form (" Ilepoit of Committee 

 appointed to explore the Marine Fauna of the South Coast of Devon : No. 2," 

 Brit, Assoc. Eeport, 1867, p. 283, pi. iii. fig. 4). 



It may readily be supposed, after having seen the animal withdraw from 

 the old shell, that we arrive at a full knowledge of how the act is performed. 

 It may appear comparatively an easy natural process to withdraw the soft 

 and yielding body from the hard and rigid case ; and this may be so when 



