On EUROPEAN SPIDERS. 21 
strictly comparative, a quality we do not often meet with in the descriptions 
of this group of animals; and we probably do not say too much when we 
assert, that WESTRING surpasses all his predecessors in the accuracy and 
sharpness of his descriptions, and that his work, in its descriptive character 
— if we overlook the occasionally somewhat lengthey diagnoses !) — may 
be considered as a model for those who come after him. 
ting-paper. The head of another insect-pin of about the same substance having been 
cut off, the blunt end is introduced into the severed abdomen (through the opening 
caused by the abscission) up to the spinners, and is fastened by its point into the 
above-named shaft. By holding the pin a moment in the flame of the light, the 
abdomen is easily made to sit fast upon the little spit. The glass cylinder is then 
taken in the left hand and holden horizontally over the flame; with the right hand 
the spider’s abdomen is introduced into the open end of the cylinder, and holden 
there immediately over the flame. In consequence of the heating of the air in the 
cylinder, the abdomen is gradually hardened, under which process it must be turned 
on all sides and brought nearer to or removed farther from the heated glass as 
occasion may require; but care must be taken not to employ too great a heat, as 
the abdomen would then be burned or erack, nor too small a heat, as the skin 
would in that ease wrinkle and collapse. One must every now and then try with 
a fine needle whether the abdomen be everywhere firm so as not to yield to pressure: 
and the hardening process must be continued till this is the case. The pin (spit) 
is now cut off obliquely (so as not to be too blunt), at such distance, that a portion 
of about ?/, the length of the cephalothorax is left standing out from the abdomen. 
By means of the tweezers this portion of the pin fixed in the abdomen is introduced 
into the cephalothorax through the opening made by clipping the petiolum. When 
the abdomen and cephalothorax have been thus reunited, and placed in their natural 
position, the pin for mounting the spider is stuck perpendicularly into a slice of 
cork, so that the spider remains at a short distance from the cork; the legs are 
extended and fastened by means of pins in their natural position (as in the speci- 
mens in my collection), or else somewhat bent under the body (as in WEsTRING'S 
collection, in which case they are not so easily broken off); in this condition the 
animal must remain in a dry place, until the cephalothorax and legs are completely 
dry, when it is ready to be placed in the collection. Spiders thus prepared are as 
easily and conveniently examined as insects impaled in the usual manner; but if 
one has besides a collection in spirits, so much the better. Very few species (e. g. 
some of the genus Xysticus) lose a little of their colour in hardening: nearly all 
others, if rightly manipulated, remain entirely unchanged. 
1) Originally diagnosis was looked upon as synonymous with "differentia speci- 
fiea", i. e. a definition comprising the marks necessary and suffieient to distinguish 
the species from all other species belonging to the same genus. But such a definition 
is possible only when all the species of the genus are known, which is far from 
being always the case: and, in the case of genera containing many species, at any 
rate such definitions would mostly be too long to be of any great practical utility. 
