220 Mr. Blackwall oti the Number and Structure of 



I denominate the superior spinnets ; tiiat furtliest removed from the anus, the 

 inferior spinners ; and the mammulce placed between these extremes, the in- 

 termediate spinners ; distinguishing them, wlien tliere are two pairs, by pre- 

 fixing the terms superior and inferior. Exceedingly fine moveable papillre or 

 spinning tubes, for the most part dilated at the base, occur at the extremity 

 of the nianunuloe, 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, Leenwenhoek, Treviranns, 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 an) 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 mammulce are abundantly sui)plied ; 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 papilla? or spinning-tubes, I must 

 regard the latter as solely instrumental in the emission of the silken filaments 

 transmitted from the mammidce ; indeed, interspersed among the papilhe, 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 papilhe 

 connected with the spinning mammuke of spiders ; but in every instance with 

 which I am acquainted they appear to be estimated nuich too highly ; in 

 point of fact, they vary greatly in nund^er in different species, and also differ 

 considerably in size, not only in individuals of the same species, but often 

 even on the same mamnuila;. 



Among British spiders, the larger species of Epeirœ have the mammulœ 

 most amply provided with papillte ; it is probalde, liowever, that the total 

 nuudjer does not greatly exceed a thousand even in adult females of Epeira 



* Cyclopaedia of Auatomy and Physiology, p. 209. 



