Ml*. J. Blackwall on the Physiology of the Araneidea. 173 
XVII.' — Resea7'ches having for their object the Elucidation of cer- 
tain Phcenomena in the Physiology of the Araneidea. By John 
Blackwall, F.L.S. 
Since an epitome of my researches into the structure, functions 
and oeconomy of the Araneidea was published in the ^ Report of 
the Fourteenth Meeting of the British Association for the Ad- 
vancement of Seienee, held at York in September 1844,^ and in 
the fifteenth volume of the ^Annals and Magazine of Natural 
History,^ I have repeated, with slight modifications, several of 
the experiments relative to the reproduction of the limbs of spi- 
ders therein detailed, and as they appear to present some in- 
teresting results I shall give them in the order of their oceur- 
rence, together with the inferenees deduced from them. 
1. The digital joint of the left palpus of an immature female 
Tegenaria civilis was amputated on the 28th of April 1845. On 
the 24th of the following June the spider cast its integument and 
the left palpus was reproduced ; it was unsymmetrical in form, 
the axillary, humeral and cubital joints being equal in size to the 
corresponding parts of the right palpus, but the radial and digi- 
tal joints were small. The digital joint of the new palpus was 
amputated on the 28th of June, and the limb was again restored 
at the suceeeding moult, which took place on the 18th of August 
in the same year, when the radial and digital joints, though en- 
larged, were still inferior in size to those of the right palpus. 
2. A very young female Tegenaria civilis had the right poste- 
rior leg detaehed at the coxa on the 30th of April 1845 by means 
of a fine pair of forceps. It moulted on the 19th of June, when 
the right posterior leg, of a small size, was reprodueed. On the 
26th of the same month the new leg was detached at the eoxa, 
and was reproduced on the 30th of July, when the spider again 
cast its integument. This leg was detached in like manner on 
the 5th of August, and was reproduced on the 11th of September, 
at which period also the spider moulted. On the 14th of Sep- 
tember the leg last restored was detaehed, and was reproduced 
on the 8th of November, when the spider underwent its final 
moult and arrived at maturity. The right posterior leg, which 
was reproduced four times, maintained its symmetry inviolate 
through the whole of these ehanges ; but though its dimensions 
were enlarged with the growth of the spider at eaeh successive 
ehange of integument, yet they were always greatly inferior to 
those of the eorresponding leg on the opposite side. 
3. On the 28th of June 1845 a very young female Tegenaria 
civilis had the right anterior leg detached at the eoxa. It moulted 
on the 6th of July, but the coxa only of the mutilated leg Avas 
