Mr. J. Blackwall on the Physiology of the Araneidea. 173 



XVII. — Researches having for their object the Elucidation of cer- 

 tain Phenomena in the Physiology of the Araneidea. By John 

 Blackwall, F.L.S. 



Since an epitome of my researches into the structure, functions 

 and ceconomy of the Araneidea was published in the ' Report of 

 the Fourteenth Meeting of the British Association for the Ad- 

 vancement of Science, 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 occur- 

 rence, together with the inferences 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 succeeding 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 detached 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 reproduced. On the 

 26th of the same month the new leg was detached at the coxa, 

 and was reproduced on the 30th of July, when the spicier 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 detached, 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 repi'oduced four times, maintained its symmetry inviolate 

 through the whole of these changes ; but though its dimensions 

 were enlarged with the growth of the spider at each successive 

 change of integument, yet they were always greatly inferior to 

 those of the corresponding 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 coxa. It moulted 

 on the 6th of July, but the coxa only of the mutilated leg was 



