_ dom. Thus we have the animal kingdom in contrast with and 
in distinction from the vegetable and mineral kingdoms. 
This great whole, the animal kingdom, is subdivided into 
seven great groups or su5-kingdoms, to one or other of which 
every SIME eneen to us belongs. ; 
__ Each of these sub-kingdoms (like every more subordinate zoo- 
_ logical group) is characterised and defined by certain points of 
structure possessed by the animals which compose it and which 
serve to distinguish them. . 
Thus, if we take up an earthworm we see that its body is com- 
_ pesed of a series of similar segments or rings placed one behind 
_ the other, and we know that it belongs to that great sub-kingdom 
_ of ringed animals termed Anzzudlosa. 
If we examine a thousand-legs or a wood-louse we see that 
here again the body is evidently composed of a series of rings or 
segments, to most of which jointed legs are attached. A suc- 
cessive survey of a lobster, a scorpion, a bee, a beetle, or a 
butterfly will reveal to us that all these creatures, however diffe- 
rent in other respects, all belong to the same ringed type, i, 
that they are a'l members of the sub-kingdom Axnulosa, which 
7 a 
G. 2.—Tadpoles in different stages of development, from those just hatched 
(x) till the adult form is attained (8). 
contains all such animals, all insects, together with spiders, 
earthworms, and leeches. 
Another great sub-kingdom called J/o//usca contains all snails, 
slugs, cuttle-fishes, and creatures of the oyster and scallop class, 
Such animals have not the body composed of a series of similar 
segments, but are united by characters less obvious indeed, but 
as distinctive. 
A third sub-kingdom called A/ol/uscoida is made up of the 
sea-squirts, or Ascidians (sometimes called Tunicates) and lamp- 
shells, together with minute animals living in water in compound 
aggregations, like the /vustra (or Sea-mat) so common on our 
coasts, the surface of which is pitted with minute depressions, in 
each of which a minute animal had in life its abode—as doves in 
a dove-cot, if we imagine each fastened in its cell by natural 
wth, 
A fourth sub-kingdom, Azuloida, is composed of such 
animals as star-fishes and sea-urchins, together with internal 
parasites (tape-worms, &c.) and their allies. 
The fifth sub-kingdom is named Caventerata, and contains all 
sea-anemones, jelly-fishes, Portuguese men-of-war, polyps, and 
coral animals, these being the little creatures which have formed 
the atolls (or coral islands) of southern seas, and the vast reefs 
| order. 
Gt 
which stretched for so many hundred miles on the earth’s 
surface. 
The sixth sub-kingdom, Frofesoa, comprises the Sponges, the 
Infusoria, and all the lower forms of animal life. 
Now the whole of these six sub-kingdoms may be contrasted 
with the last and seventh, which bears the name Vertebraia, 
from which they all differ in several important particulars, and 
therefore they are often spoken of hy the common and con- 
venient term Zrvertebrata. 
When we examine a fish (such as a sole, a herring, ora 
mackerel), one of the first things likely to be noticed by us on 
dividing it, is a solid structure—tke backbone—extending from 
the head to the tail, and coated externally by the flesh. 
This backbone is soon seen to be made up of a number of 
pieces jointed together. Each piece is called in natural 
history a vertebra, and every animal in which such a 
structure is found, is called, on that account, a Vertebrate 
animal. 
Now every kind of beast and reptile agrees with these fishes 
in the possession of the vertebrate backbone, as well as in a 
variety of other important characters, which constitute the 
definition of the sub-kingdom Vertebrata. 
Thus in the development of the egg of every Vertebrata (such 
ég. as in that of the fowl), the first indication of the future 
animal, is the appearance on part ofits surface of a minute 
longitudinal furrow called the primitive groove. Next the 
margins of this groove ascend to meet together above, thus 
enclosing a canal, the lining of which becomes thickened and 
transformed into no less important a structure than the brain 
and spinal marrow. 
Concomitantly with the development of this canal, there is 
found, immediately beneath it, a little gelatinous rod enclosed 
in a membraveous envelope, and called the xofochord, or chorda 
dorsalis, It is this structure which is subsequently developed 
and becomes the backbone. ‘ 
Ancther singular condition is invariably presented in the 
development of every vertebrate, whether the structures formed 
are transitory or permanent. 
This condition is the appearance of a certain series of open- 
ings formed at the side of the neck, and which, in fishes, 
remain permanent as the gill openings. These openings are 
termed visceral clefts, and lead from the exterior into the throat. 
The solid pillars (or intervals) between the clefts are called 
visceral arches, and in creatures (e.g. fishes) which develop gills 
upon them, dranchial arches. 
In all vertebrates again (unlike insects or spiders) there are 
never more than four limbs, and these are supported by bones, 
orcartilages, which are clothed externaliy with flesh, and are not 
moved by muscles placed within the hard parts, as is the case 
with lobsters, insects, and all their allies. 
The heart in all vertebrates, consists of at least two distinct 
cavities, and sends forth blood into a system of arteries, thence 
it is brought back again to the heart by other vessels termed 
the veins. On its way back to the heart, however, some of the 
veins carry blood to be redistributed in the liver, forming what 
is called the Zorta/ circulation. - 
Tn all the points above enumerated, the Frog (as we shall 
shortly see) fully agrees with beasts, birds, reptiles, and fishes, 
and thus shows that it differs from the immense majority of 
animals—the /vertebrata—and pertains unmistakeably to the 
seventh sub-kingdom of animals—the Vertebrata. 
Now every sub-kingdom of animals is further divided into a 
greater or lesser number of subordinate (though still Jarge) groups, 
termed classes. Each class is again subdivided into a certain 
number of smaller and more subordinate groups, each of which 
is termed an order. Each order is made up of families, each 
family being of course, smaller, and more subordinate than an 
Eyery family consists again of still more subordinate 
groups, each of which is termed a genus. And every genus 
comprises one or more sfecies. 
In zoology, every animal bears a name composed of two 
words. The first of these is a substantive, and denotes the 
genus to which any given animal belongs, The second word 
is an adjective—or a word used in an adjective sense—and 
denotes which species of the genus that given animal is. Thus 
the Chimpanzee is called Zroglodytes niger, it is the species 
Niger of the genus TZroglodytes, which genus contains also 
another species, namely, the Gorilla, ; 
St, GEORGE MIvART 
(To be continued.) 
