[239.42 
XIII. On the Number and Structure of the Mammulæ employed by Spiders in 
the Process of Spinning. By Joun BrackwaLr, Esg., F. L. S. 
Read June 5th, 1838. 
WHEN 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 mammulæ 
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 compeiled 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 mammulæ, 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 
