20 T. THORELL, 
30 to Thomiside, 35 to Lycoside and 31 to Attide. Not only the species, 
but also the genera and families are in this work characterized in detail: 
by this the author has been enabled to avoid the error of taking up in the 
description of the species a number of distinctive marks common to whole 
series of species, an error, which makes the descriptions given by sundry 
other writers so deficient in characteristics, in spite of their often wearisome 
prolixity. WESTRING has succeeded in finding sharp and certain distinctive 
marks for the species he describes: we would especially call attention to 
the excellent characters he has discovered in the different number and di- 
stribution of the spines on the extremities. Equally important are the di- 
stinguishing features pointed out by WESTRING in his detailed descriptions 
of the males’ palpi: nor has he quite overlooked the circumstance, that 
similar sharp characteristics may be found by studying the external sexual 
organs of the females. What immediately strikes a reader on looking 
into WESTRING’s book, is the singular diligence and conscientiousness that 
it evinces: his descriptions have not been made independently of each other, 
they have not been written down once for all as the different species came 
under the author’s eye, but they are the result of most accurate and many 
times repeated comparisons of the various species 1). They have thus become 
1) WESTRING’s rigorous comparative treatment of the Swedish spiders has been 
considerably facilitated by the method in which his collection of spiders is preserved. 
He does not preserve his spiders in spirits, but impaled upon pins, after having first 
been dried by a process invented by himself and described with full details in his 
paper: "Anvisning att ändamålsenligt insamla och conservera Arachnider, fórnámli- 
gast med afseende 4 spindlarne.” We shall very briefly describe this method, which 
it is true at first seems difficult and tedious, but which one, after a little practice, 
finds as easy as it is appropriate. It is a characteristic of the method that the 
spider's abdomen, and that part only of ist body, is hardened by heat. The following 
simple instruments are required for the operation: 1:0, a glass cylinder of about 1” 
or 1'/," diam. and about 4" long, one end of which is closed with a cork: in this 
cylinder the spiders abdomen is hardened over the flame of a candle; 2:0, a small 
and very fine pair of scissors, as also a stronger and coarser pair: with the former 
the abdomen is cut off, with the latter the pin, which is used as a spit; 3:0, a little 
cylindrical shaft encircled at the one end by a cylindric metal ring filled with a 
cork, in which cork the spit is fastened during the operation; 4:0, a fine pair of 
tweezers, and a few small slices of cork about 2 lines thick, insect-pins, blotting- 
paper, and a lighted candle. When the spider has been in a proper manner killed 
(e. g. by vapour of ether or by heat) it is to be impaled on an appropriate insect- 
pin passed through the right side of the cephalothorax; the abdomen is then cut off 
(the animal being holden in the half-closed left hand, in which the abdomen, on 
being separated, falls) close to the cephalothorax, and the incision is dried with blot- 
