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XIII. On the Number and Structure of tlie Mciinmulce employed by Spiders in 

 the Process of Spinning. By John Blackwalf., Esq., F.L.S. 



Read June 5lh, 1838. 



W HEN the highly curious and important function performed by the spin- 

 ning apparatus of spiders is duly considered, it will not appear surprising that 

 the attention of zootomists has been repeatedly directed to the organization of 

 parts exercising so remarkable a degree of influence upon the economy of the 

 animals to which they belong, and that the powers of the microscope have 

 contributed largely to promote the investigation of this interesting subject ; 

 but, though much has been accomplished by these researches, much yet re- 

 mains to be effected ; new facts must be elicited and prevailing errors corrected, 

 before our knowledge of the matter under consideration can be regarded as 

 exact. 



Having carefully examined the external anatomy of the spinning mammulae 

 of various species of spiders, I have been led to form opinions relative to their 

 number and structure differing essentially in several particulars from those 

 generally received ; and if, in promulgating the views which an accumulation 

 of evidence too powerful to be resisted has compelled me to adopt, I find 

 myself opposed to zoologists of the highest distinction and authority, it is, as 

 I have formerly stated on similar occasions, with every sentiment of deference 

 and respect, and with a perfect consciousness of the many and great disad- 

 vantages of the position which I occupy, that I venture to question the sound- 

 ness of their doctrines. 



All the spiders which have hitherto come under my observation have been 

 provided with four, six, or eight spinning mammulse, somewhat conical or 

 cylindrical in figure, and composed of one or more joints each: they are 

 usually closely grouped in pairs, which may be readily distinguished from 

 each other by their relative positions. The pair situated nearest to the anus 



