70 T. THORELL, 
"In the summer of 1855 I first met with Mithras paradoxus, in the 
neighbourhood of Stockholm, the only part of this country, in which it has 
been observed. July, August and September are the months in which it is 
met with full-grown. ‘The males are extremely rare, and I have as yet 
not found more than one fully developed. It was taken Aug. 5. The 
female on the contrary is pretty common, and is met with principally in 
woods of trees of the fir kind, especially in pine woods. Between the dry 
bare branches of two neighbouring trees, she spins a strong thread in a 
horizontal direction, from a point of which she afterwards draws obliquely 
downwards three other threads, which form equal angles with the original thread 
and each other and le in the same vertical plane. These four threads form 
the radii of the web; over them are laid concentric cross-threads, 16—22 
in number, and tolerably wide apart. The loose net thus constructed forms 
a circular sector of about 45 degrees with a radius of a foot or more. It 
is therefore very large in proportion to the spider itself. The animal does 
not build itself any shelter or nest near the web, but hangs on the first-named 
horizontal thread that bears the web, near one of the twigs to which it is 
fastened, and at a considerable distance from the common point of inter- 
section of the radii. The identity of colour between the animal and the dry 
branches causes it not to be so easily perceived: if disturbed, it draws in 
its legs and lets itself down to the ground. Its movements are slow and 
sluggish: the prey, which has fastened in the web, is spun into an enve- 
lope of silk, before it is devoured — a process employed, as far as I am 
aware, only by the Æpeiroidæ (according to Lucas also by Uloborus).” 
"Although the web made by Mithras paradowus is so peculiar and 
so unlike that of every other known species of spider, it is easily seen from 
the description, that it cannot be looked upon as any separate and inde- 
pendent form of web, but must be classed under the head of the known 
so-called geometrical nets of the Epeiroide. Here, as with them, it con- 
sists of radii diverging from a point, united by threads running concentri- 
cally; the differenee is simply that, whereas with the other species belong- 
ing to the family it forms a closed circle, with Mithras it is but .a 
circular sector. A transition to this latter form may in a certain sense be 
looked for in the case, of which one sometimes meets with examples, 
where, in the common cireular net, the interval between two radii is 
left open, by the circular threads being terminated at these radii?. Not 
1) Another more evident transition is described by Darwin (Journal of Resear- 
ches etc. during the voyage of the Beagle, p. 42) in the following words: "In a 
