hough they lived during the trias period--they possessed a very
highly developed jaw. From the primary mammal arose the pouched animals
(marsupialia). Numerous representatives of this group still exist:
kangaroos, pouched rats and pouched dogs. The marsupial animals
developed, very probably, in the mesolithic epoch (during the Jura) out
of the cloacal animals; by the division of the cloaca into the rectum
and the urogenital sinus, by the formation of a nipple on the mammary
gland, and the partial suppression of the clavicles.

[Illustration: FIGS. I and II.--The Ceratodus Forsteri occur in the
swamps of Southern Australia. Form transition between fishes and
Amphibia.--_Haeckel._]

[Illustration: FIG. I.--Represents the Gilled Amphibians (Soyobranchia).
The Axolotl (Siredon pisciforme), after Tegetmeier. The ordinary form
with persistent branchiae.]

[Illustration: FIG. II.--Proteus Anguinus. Europe.--_Orton._]

[Illustration: FIG. III.--Represents the Tailed Amphibians (Soyura).
Great Water-Newt (Triton cristatus), after _Bell._]

From the marsupialia originated a most interesting small group of
semi-apes (prosimiae), for they are the primary forms of genuine apes and
consequently of man. They developed out of handed or ape-footed
marsupials (pedumana), of rat-like appearance, by the formation of a
placenta, the loss of the marsupium and the marsupial bones, and by the
higher development of the commissures of the brain. The still-living
short-footed semi-ape (brachytarsi), especially the muki, indie and
lori, possess possibly a faint resemblance.

Out of the semi-apes developed two classes of genuine apes; but as the
narrow-nosed or catarrhini class are the only ones related to man, the
others will not be considered. These narrow-nosed apes originated by the
transformation of the jaw, and by the claws on the toes changing into
nails. The still-living long-tail nose-apes and holy apes
(semnopithecus) probably resembled the oldest ancestors of this group.

The tailed apes by the loss of their tail and some of their hair
covering, and by the excessive development of that portion of their
brain above the facial portion of the skull, developed into the man-like
apes (anthropoides)--such as the gorilla and chimpanzee of Africa, and
the orang and gibbon of Asia. The human ancestors of this group existed
during the miocene period. From the anthropoides developed the ape-like
men (pithecanthropi) during the tertiary p