312 OBSERVATIONS ON THE 
tached portion of the mutilated part; for if a leg be 
amputated near the middle of the metatarsus, the 
coxa, femur, and tibia will be of the same dimensions 
as those joints of the corresponding leg on the oppo- 
site side, but the metatarsus and tarsus will be very 
diminutive; should the excision be made near the 
anterior extremity of the tibia, then the size of the 
coxa, femur, and genual joint will be normal, but that 
of the tibia, metatarsus, and tarsus will be very ab- 
normal. These curious results 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 which they are developed, and that 
restored legs and palpi are never symmetrical except 
when developed in the undetached coxa and axillary 
joint respectively. 
Tn order to obtain a satisfactory explanation of the 
phenomena 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 absolutely new 
organs resulting from the vital functions of assimi- 
lation and accretion; indeed the renewal of a re- 
peatedly 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 restoration, present difficulties which do not admit 
