ON THE ANATOMY OF THE ARANEIDEA. 157 
is easy to calculate its altitude above the earth, which must have been about 
43 miles. A few days afterwards, the same guard, Joseph Hill, sent me the 
_ following letter and extract from the ‘Warder’ Dublin newspaper of Satur- 
_ day the 10th, which confirms Hill’s accuracy, as the correspondent of the 
_ Warder’ must have seen it on the opposite side of the place where it had 
_ been vertical from what we did :— 
* Belfast, 12th October, 1840. 
4 Sir,—I had the pleasure also of seeing this phenomenon the same time 
_ as Correspondent. I was about 53 miles on this side of Dublin when it hap- 
pened.— Yours, &c., Josepu Hixx, Mail Guard. 
‘Extraordinary Appearance inthe Sky.—( From a Correspondent.) —About 
a quarter before ten o’clock on Wednesday, at an immense altitude, a white 
ball of fire appeared in the north-eastern part of the sky for a moment, and 
shot downwards, illuminating the whole heavens, and causing an extraordi- 
_ hary sensation in those who witnessed it before its descent. The ball was 
tinged with a beautiful violet blue —From the ‘ Warder’ of Saturday, Octo- 
: 
: ber 10, 1840.” 
On some Points in the Anatomy of the Araneidea, or true Spiders, 
especially on the internal structure of their Spinning Organs. By 
R. H. Meapz, F.R.C.S. 
[A Communication ordered to be printed entire among the Reports.] 
Ir is not my intention in the present communication to enter generally into 
the anatomy of spiders, but to confine myself to an account of the arrange- 
ment and structure of the parts contained in the abdomen; and more espe- 
cially to describe the glandular organs by which the silk forming their webs, 
is secreted. 
I was led to undertake this investigation by the hope that an accurate exa- 
mination into the minute anatomical structure of the spinning organs might 
clear up some important differences of opinion as to their functions. Martin 
Lister, Cuvier and others, contend that spiders have the power of forcibly 
ejecting the fluid which forms the silk from their spinnerets; and are thus 
able to propel a thread to a considerable distance, and in any direction. 
Both the above-named naturalists state that they have distinctly seen them 
shoot out their webs, but Mr. Blackwall (the greatest living authority on 
Arachnology ) denies that they have any such power, and says that the tena- 
cious fluid is simply emitted from the extremity of the abdomen by pressing 
it against some fixed point, and then drawn out into a thread by a current of 
air, and wafted to some neighbouring object to which it adheres, or left 
floating in the atmosphere. Should my researches fail to clear up this inter- 
esting question, they may tend to elucidate some other curious points con- 
hected with the functions of the spinning organs,—such as the power which 
spiders have of forming different kinds of threads from the same spinnerets, 
some of which are adhesive, while others have no viscidity, but simply form 
a framework to support the others. 
_ I met with considerable difficulties in the course of my investigations, had 
to make numerous dissections, and at Jast was unable to arrive at satisfactory 
conclusions on many points; for the organs are so small and delicate, and 
become so brittle when the spiders have been preserved any time in spirits, 
that it is not easy to separate them. My plan has been to dissect carefully 
in water or spirit, under a simple lens, and then to submit each portion sepa- 
rately to the action of a compound microscope. 
