220 Mr. BIackwallL on the Number and Structure of 
I denominate the superior spinners; that furthest removed from the anus, the 
inferior spinners; and the mammulæ placed between these extremes, the in- 
termediate spinners ; distinguishing them, when there are two pairs, by pre- 
fixing the terms superior and inferior. Exceedingly fine moveable papillz or 
spinning tubes, for the most part dilated at the base, occur at the extremity 
of the mammulæ, or are disposed along the inferior surface of their terminal 
joint; whence issues the viscous secretion of which the silken lines produced 
by spiders are formed. The minute apertures without projecting margins, 
described by Lyonnet, Leeuwenhoek, Treviranus, and other eminent anatomists 
and microscopic observers as likewise emitting lines*, I have failed to detect 
on the closest inspection, assisted by optical instruments possessing high mag- 
nifying powers; I am under the necessity, therefore, of withholding my assent 
from an opinion which, in consequence of the celebrity of its advocates, is 
very generally adopted. It is true that I can discern small pores with which 
the mammulæ are abundantly supplied ; but as they are distributed over their 
entire surface, and occupy the intervals between their bases, from which no 
lines are ever seen to proceed ; moreover, as I have never, under any circum- 
stances, perceived the viscous matter of which the lines are composed issuing 
from these pores, but uniformly from the papillæ or spinning-tubes, I must 
regard the latter as solely instrumental in the emission of the silken filaments 
transmitted from the mammulæ ; indeed, interspersed among the papillæ, as 
the pores constantly are, they would prove a source of the utmost inconveni- 
ence were they endowed with the property which seems to have been ascribed 
to them. 
Attempts have been frequently made to ascertain the number of papillæ 
connected with the spinning mammulæ of spiders; but in every instance with 
which I am acquainted they appear to be estimated much too highly; in 
point of fact, they vary greatly in number in different species, and also differ 
considerably in size, not only in individuals of the same species, but often 
even on the same mammule. = 
Among British spiders, the larger species of Epeire have the mammule 
most amply provided with papillz; it is probable, however, that the total 
number does not greatly exceed a thousand even in adult females of Epeira 
* Cyclopedia of Anatomy and Physiology, p. 209. 
