a 

Suborder Il]. Cumacea. 
The chief character of his small group is that 
the last 4 or 5 thoracic seginents are not covered 
by the carapace; the abdomen is long, and the eyes 
are wanting, or reduced to a pair of mere rudiments. 
Most of the species inhabit the Northern Seas. 
Suborder 1V. Stomatopoda. 
This is a small but well-marked group, which 
exhibits a superficial resemblance in form to some 
Orthopiera. 
47 
} Fig. k. Sguzlla mantis, which inhabits the Me- 
diterranean, is one of the best known species. Its 
long body resembles that of the Decapoda, from 
which it is at once distinguished by the carapace, 
which leaves the four last thoracic segments exposed. 
No less than five pairs of legs are modified into foot- 
jaws for seizing and tearing prey, and the second 
pair is furnished with a powerful dentated hand for 
striking and grasping. The three other pairs of legs 
serve for walking, and are cleft, and the abdomen 
is furnished with swimming-legs. 

Order IJ. Arthrostraca. 
The species of this Order agree with those of 
the last in the number of segments (20) into which | 
the body is divided, and of paired extremities (19), 
but they differ in the absence of a carapace. The 
eyes are not placed on stalks, but on the body itself. 
There is no metamorphosis, and the eggs are car- 
ried about by the female in cavities formed by appen- 
dages of the thoracic legs. They are small creatures, 
and many of them are land-animals, 
Suborder I. Amphipoda, 
The body is iaterally compressed, the front 
pairs of thoracic legs often end in grasping-claws, | 
the three first pairs of abdominal legs are swimming 
feet, and the three next are penicillate. The species 
are very numerous. 
Fig. 0. Gammarus pulex, the Fresh-water 
Shrimp (which name is sometimes improperly applied 
to the larve of the Dyzsczd@) is common in fresh 
water, and is frequently used as food for other ani- 
mals kept in aquariums. It is called paler, “the Flea” 
from its peculiar jerking movements. The allied 
species found on the sea-shore are called sand-hoppers. 
The Phronimide are distinguished by their wide 
head, the great pincers on the fifth pair of legs, and 
their habits. They inhabit the bodies of Sa/pde, 
in which they swim swiftly about in the sea. One 
species, P. sedentaria, is represented at fig. l. 
The Caprellide also exhibit very strange shapes. 
They are characterised by their very slender form, 
and by the rudimentary abdomen, which is reduced 
to a jointless protuberance. Caprella spinosissima, 
a very remarkable species from the Northern seas, 
and which is covered with spiny protuberances, is 
represented at fig. m. 
The Cyamide resemble the Capreliide in the 
rudimentary abdomen, but are totally different in 
Section II. 
form and habits, being parasites on the skin of 
whales. Cyamus ceti, the Whale-Louse, is represented 
at fig. n. 
Suborder IH. 
The body is vertically compressed, and the 
thoracic legs are uniformly adapted for walking or 
clinging. The organs of respiration are placed in 
delicate layers above the five terminal legs. 
The Onxztscide@, or Wood-Lice, are found on 
land in damp places, and the external plates of the 
abdominal legs form strong covers. The first pair of 
antenne is very small, and not visible from above. 
Two species are figured: Oniscus murarius, fig. p., 
and forcellio scaber, fig. q. 
In the allied genus Armadillo, the species roll 
themselves up into a ball. Several species of Ovzs- 
cid@é are water-animals. Asellus aguaticus is an in- 
habitant of fresh water, but most of the species are 
marine, including Lzmxoria terebrans, which bores 
in timber. 
The Cymothoide may be known by their short 
abdomen, grasping legs, and large size. They attach 
themselves by the sucking parts of their mouth to 
the skin or within the mouth of fishes. Ceratothoa 
trigonocephala has been figured as a representative 
of this family (fig. r). 
lsopoda. 
The Bopyride are the first family to exhibit 
the influence of parasitism, which proceeds to such 
an extent as to obliterate all characters of its class 
in the mature animal, so that nothing but the course 
of its development indicates its Zoological position. 
At the same time the sexes differ greatly, as the 
very small unattached males preserve the appearance 
of woodlice. The large females which live parasitically 
in the gill-cavities of shrimps, or the body-cavities 

of crabs, lose their eyes and the segmentation of the 
| body, and look like ugly swellings or tubes. 
Entomostraca. 
The lower groups of the Crustacea are placed | mostraca, no matter how different may be the fully- 
together under this name, although there is no general 
character which will apply to all the very different 
forms which are included under it. They all agree, 
however, in their development, for they undergo 
metamorphoses, and quit the egg in the so-called 
Nauplius form, which is the same in all the Ayxfo- 
developed animals. The freely swimming larve called 
Nauplius, have an oval body, a single eye on the 
forehead, and three pairs of limbs. They pass 
through numerous changes of form before reaching 
the final stage of their development. 
