176 Mr. J. Blackwall on certain PJuenomena in the 
1847. The spider moulted on the 14th of the same months when 
the stumps only of the mutilated limbs were produced. On the 
7th of the following July it moulted again^ at which time the 
left posterior leg, of small dimensions, but symmetrical in form, 
was restored ; the right posterior leg was also restored, but the 
metatarsus and tarsus were disproportionately small. 
13. On the 14th of June 1847 the right posterior leg of an 
immature female Agelena labijrinthica was amputated near the 
middle of the metatarsus. The spider cast its integument on 
the 2nd of the ensuing July, when the mutilated limb was re- 
produced. The coxa, femur and tibia were equal in size to the 
corresponding parts of the left posterior leg, but the metatarsus 
was very small, and the tarsus was extremely diminutive. 
Experiments 2, 3, 4 and 9 serve to establish the fact, that if a 
leg of an immature Tegenaria civilis be detached at the coxa four 
or even six times consecutively, it may be reproduced at each 
succeeding moult the spider undergoes. This frequent renewal 
of the same part seems to warrant the conclusion that a repro- 
duction of the limbs of the Araneidea generally, irrespective of 
mutilation, actually occurs whenever a change of integument 
takes place ; and this view of the subject, which probably might 
be extended to numerous subdivisions of the Articulata, derives 
additional support from evidence supplied by the other experi- 
ments. 
That the dimensions of reproduced limbs are in inverse ratio to 
the extent of the injury previously inflicted on the parts is mani- 
fest from experiments 1, 3, 10 and 12 ; thus, palpi and legs de- 
tached at the axillary joint and coxa are usually symmetrical, but 
diminutive, w hen reproduced ; while those amputated at the arti- 
culation of the digital with the radial joint, and near the middle 
of the tibia or the metatarsus, on being restored are always very 
much larger and unsymmetrical ; in point of fact, the develop- 
ment of the new limb depends upon the capacity of the unde- 
tached portion of the mutilated part ; for if a leg be amputated 
near the middle of the metatarsus, as w as the case in experiments 
5, 12 and 13, the coxa, femur and tibia wnll be of the same di- 
mensions as those joints of the corresponding leg on the opposite 
side, but the metatarsus and tarsus will be very diminutive; 
should the excision be made near the anterior extremity of the 
tibia, as in experiments 6, 7 and 8, then the size of the coxa, 
femur and genual joint wdll be normal, but that of the tibia, 
metatarsus and tarsus will be very abnormal. These curious re- 
sults plainly demonstrate, that not only reproduced limbs in their 
totality, but that particular joints also are limited in their dimen- 
sions by the capacity of the undetached portion of the mutilated 
part in w'hich they are developed, and that restored legs and 
