CHAPTER VII. 
The Jointed Animals,— concluded. 
The Sea-Spiders, King-Crabs, and Crustaceans,— 
Classes Pantopoda, Gigantostraca, and Crustacea. 
The animals belonging to the first of the three classes named above present 
such a marked general resemblance to the true spiders, that they have been 
included in the same class. On the other hand, from their marine mode of life, 
some writers have come to the conclusion that their affinities are rather with 
the Crustaceans. As a matter of fact, it appears impossible to affiliate them with 
either of these groups, and the general opinion is that they are entitled to form 
a class by themselves. In all these creatures the adult is provided with four 
pairs of well-developed legs, composed of a large and varying number of segments, 
and each tipped with a single 
claw. These limbs, which are 
often exceedingly long and 
slender, radiate from the sides of 
the cephalothorax, which is pro¬ 
duced into stalks for their support. 
In front of these limbs, and 
attached to the headpiece, are 
sometimes three additional pairs of 
appendages. Hence the full com¬ 
plement of limbs is seven, and not 
female of slender sea-spider, with eggs (much enlarged). pairs as in the true spiders. 
The first pair of appendages, form¬ 
ing the mandibles, are short and often pincer-like; the second pair, or palpi, being 
also short; while the third pair, which are only developed in the females, are 
shorter than the true legs, and, from their function, are termed the egg-bearing 
legs. In some cases, however, these three pairs of appendages have entirely 
disappeared, as in the shore-spider (Pycnogonum littorale). Projecting forwards 
from the front end of the body is a long rigid beak, or proboscis, at the 
tip of which the mouth is situated. This beak is not formed by the fusion 
of limbs, like that of the ticks, but results from the great development of the 
area immediately around the mouth. The cephalothorax is divided into four 
distinct segments, of which the first, or head, supports the first four pairs of 
appendages, and has on its summit a pair of eyes, while the rest bear the three 
posterior pairs of limbs. Attached to the last of these segments, and projecting 
