4 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 
from, it will be easier to trace the connection existing between 
them, and the relation which they bear to the primal form and 
to each other. 
Fig. 1. Represents the archetype—according to Messrs. 
Thorell and Poecoek—an Arthropod with a body consisting of 
18 somites; the anterior 6 of which are provided with large 
appendages for locomotion and grasping; having a eluster of 
median eyes, and a group of lateral eyes on each side. In 
recent Arachnida, the number of eyes varies from 2 to 8, dif- 
ferently disposed in the various genera. One species of whip- 
scorpion is eyeless; and a spider is found in the Mammoth eave 
in Kentucky, in which the eyes are completely atrophied. The 
head and thorax of the archetype are fused together. Hach of 
the 6 succeeding somites bears a pair of small ventral appen- 
dages; these have become lost by the 6 posterior somites. 
Now, it is obvious that this body was very unwieldly, and 
consequently ill-suited to the needs of a predaceous animal. 
By means of the succeeding diagrams it may be shown in detail 
how each order of the Arachnida have departed from and im- 
proved this useless body, so as to best suit the mdividual con- 
ditions of existence. And it will be of advantage to bear in 
mind that Evolution is as much a process of elimination, as of 
elaboration and addition. 
Fig, 2. The Scorpions approach most closely to the original 
form; and in them the 5 unwieldly posterior somites become 
narrowed into the so-called “‘tail’’ (really a part of the abdo- 
men), having at its end a post-anal selerite or sting. The 4 
posterior appendages of the 6 abdominal somites become merged 
into the stigmata of the lung-saes; the second pair are modified 
into those curious organs of perception, the pectines or combs, 
which are peculiar to this group. 
Fig. 3. In the Whip-tails (Uropygi1), the whole abdomen is 
ereatly reduced in leneth, and the 3 posterior somites are nar- 
rowed to support the multi-articulated, harmless telson or whip, 
corresponding to the ‘‘sting’’ of the scorpion and the swim- 
ming-plates of the lobster. A deep constriction separates the 
cephalothorax from the abdomen, and two of the lung-saes dis- 
appear. 
Fig. 4. In the Phrynichide (Amblypyei), the whole body is 
shortened into a kidney shape; the “‘tail’’ entirely disappears; 
and the scorpion’s pincers are transformed into a pair of terri- 
ble grappling-hooks. The first pair of legs become very long 
and antenniform; and are no longer used as walking-legs, but 
as tactile organs, like the antenne of insects. ,,  , 
Fig. 5. In the Arane or true spiders, there is a deep con- 
striction in the shape of a stalk or pedicel between the cephalo- 
