177 
Physiology of the Araaeidea. 
palpi are never symmetrical except when developed in the unde- 
tached coxa and axillary joint respectively. 
In order to obtain a satisfactory explanation of the phseno- 
mena stated above, it must be conceded that the limbs of spiders 
produced at each successive moult, from the period at which the 
animals quit the cocoon till they arrive at maturity, are abso- 
lutely new organs resulting from the vital functions of assimila- 
tion and accretion ; indeed, the renewal of a repeatedly detached 
leg at each succeeding change of integument, and the circumstance 
of the dimensions of entire limbs or portions of limbs depending 
upon the space allowed for their development at the time of re- 
storation, present difficulties which do not admit of a solution on 
any other physiological principle that I am aware of. 
Sometimes the stump only of a partially amputated leg is pro- 
duced at the succeeding moult, especially when the injury has 
been inflicted but a short time previously to the change of inte- 
gument, as may be seen on referring to experiments 3, 9 and 12. 
As the formative process in this case must have made consider- 
able progress before the excision of the part was effected, there is 
nothing extraordinary in the result ; but a similar consequence 
occasionally ensues when the partial amputation of a leg takes 
place very soon after a change of integument, before the forma- 
tive process can be supposed to have commenced ; experiment 4 
presents an instance of this kind ; a much more remarkable one, 
however, is given in the ^ Annals and Magazine of Natural 
History,^ vol. xv. p. 233, experiment 12, from which it appears 
that the stumps only of the palpi of a young male Linyphia cauta 
were produced at two consecutive moults after the parts had suf- 
fered mutilation, though several legs of the spider, mutilated at 
the same time, were renewed at the next moult after the infliction 
of the injury. 
If these facts are inexplicable at present upon the principle of 
the reproduction of lost parts by the Araneidea which 1 have 
been advocating, it may be attributed to the obscurity in which 
they are involved, and as they are decidedly opposed to every 
other view of the subject, it is not necessary to notice them more 
particularly in this place. 
1 avail myself of the opportunity afforded by this communica- 
tion to correct a statement contained in the epitome of my re- 
searches into the structure, functions and ceconomy of the Ara- 
neidea, (Report of the Fourteenth Meeting of the British Asso- 
ciation for the Advancement of Science, held at York in Septem- 
ber 1844, p. 73; and the Annals and Magazine of Natural 
History, vol. xv. p. 234,) to the effect, that if part only of a 
limb of a spider be amputated, as the tarsus of a leg or the digi- 
tal joint of a palpus, all the joints of the limb when reproduced, 
Ann. ^ Mag. N. Hist. Ser. 2. Vol. i. 12 
