290 Dr. Heinekcn on the casting off and 



I suspect, therefore, that where it can be accompHshed by the former, it 

 will, be retained, but when only by the latter, thrown off at the suture; 

 of the power of selection on the part of the animal, there can, T think, be 

 no doubt ; the spiders which cast off the crushed limbs were hunters ; 

 those which retained them, web-makers : the former, perhaps, have a 

 stronger inducement to the act, as an inert and powerless joint would be a 

 greater inconvenience to them than the loss of the whole limb ; indeed, 

 under all circumstances, probably (but it requires to be substantiated by 

 experiment) such is the case ; a tveb-maker being of stationary liabits, 

 and generally concealed, is less liable to accidents than a hunter, (which 

 is constantly on the move, and as generally exposed,) and therefore, per- 

 haps, less prompt when they occur. 



It has not, as far as I am aware, been generally supposed that the 

 power of reproducing limbs in Spiders is restricted to certain 'periods of 

 their lives, but the following experiments will, I think, lead to the con- 

 clusion, that as soon as the animal ceases to moult its skin, or in other 

 words, becomes an adult, its limbs cease to be reproduced,* and a soli- 

 tary example,t as far as it goes, induces me to think that after that pe- 

 riod, but at a very protracted interval (for it never took place within the 

 time that I succeeded in keeping them alive) the stump becomes attenu- 

 ated by absorption, so as to be a tolerable substitute for a perfect joint, 

 but does not acquire claws, &c. which all the reproduced limbs or ex- 

 treme joints possess immediately they appear. For the sake of brevity, 

 and to avoid the appearance of wishing to multiply the examples of re- 

 produced joints (as I shall use some of those already quoted for that pur- 

 pose, in substantiating the facts regarding moulting J I shall merely state 



* Finding that in some reproduction took place very readily, and at a rea- 

 sonable period, but that in others it altogether failed, although the animal lived 

 for months, was healthy, and even produced young, I was long completely at 

 a loss how to account for it; at last I observed an individual to go into its con- 

 cealment maimed, and come out whole, leaving a sloughed skin behind ; it im- 

 mediately occurred to me that there was a connexion between the processes, and 

 therefore probably between the periods also, and the result has proved, in my 

 opinion, quite satisfactory. 



\ An adult Epeira fasciata caught with such a stump as is described. 



