162 : REPORT—1858. 
framework of elastic filaments first constructed. The common house spider 
( Tegenaria civilis) is said to form no adhesive lines, and I have been unable 
to find any of the cartilaginous glands in its abdomen. 
We now come to the consideration of the various shaped membranous sacs, 
the ducts of which are much larger than in the cartilaginous kind, and, as I 
have shown, are furnished with a fibrous coat arranged in distinct rings. I 
have no doubt that these sacs form the fluid which constructs all the strong 
non-adhesive threads spun by spiders, and also the floating lines or gossamer, 
of the aéronautic species. In support of the latter assertion, I have found 
that two of the most common among the aérial spiders, viz. Lycosa saccata 
and Thomisus cristatus, contain these sacs in great size and number; whereas 
they are erratic species spinning no regular webs, and therefore having no 
other apparent use for them. In most other species of Lycose the spinning 
organs are in a very rudimentary state. 
I have now arrived at the most interesting, but most difficult part of my 
task, viz. the question whether there is anything in the structure of the silk- 
forming organs that will decide the question as to the power of spiders to 
eject their threads to a distance. Looking at the strong fibrous coat on the 
ducts of the membranous sacs, and the fibrous tissue surrounding the glands 
themselves, I think that they must possess a powerful contractile power, which 
may also be increased by the muscular coat of the integument enabling the 
spider to compress its abdomen: may not the striated bands of muscular 
fibres, which run in a parallel direction down the middle of the abdomen 
quite into the interior of the spinnerets, and surround the termination of the 
ducts, also assist in this object? They are not attached to the tegumentary 
coverings of the spinnerets like the other muscles, and cannot therefore be 
for the purpose of moving these processes ; their action must be to draw the 
spinnerets inwards. On examination of the pectoral muscles which connect 
the legs with the cephalothorax, and which possess great power, to enable 
the spider to perform its various active movements, I found that they pre- 
sented exactly the same microscopic appearances as the deep abdominal 
muscles, being very strongly striated; I therefore conclude that the latter 
perform some very active functions. 
In adopting the conclusion that spiders have the power of forcibly pro- 
pelling the silky fluid from their spinners, I know that Iam running counter 
to the convictions of Mr. Blackwall, for whose opinion on all points con- 
nected with Arachnology I have the greatest veneration. That patient and 
acute observer based his views upon the result of many carefully conducted 
experiments ; he found that spiders, when placed upon an upright stick which 
had its base fixed in water, could not escape when they were covered by a 
glass shade, so as to prevent any movement of the air; but when left un- 
covered, in the ordinary atmosphere of a room, they emitted a little fluid 
from their spinnerets, which was drawn out into a thread by the slightest 
current of air, and soon became attached to some neighbouring object. I 
think it very probable that a current of air may thus draw out these almost 
imponderable lines in some cases, but I consider that we cannot thus account 
for the formation of their threads under all circumstances and in all places. 
We have also the testimony of Cuvier and others, that spiders sometimes 
eject their threads simultaneously in opposite directions. Cuvier has seen 
this feat performed by a Thomisus*, and Kirby and Spence quote an obser- 
vation made by an anonymous author, who says he saw a small spider shoot 
out obliquely in opposite directions small threads, which attached themselves 
_* Regne Animal. 
