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TABLE OF CONTENTS.

1. The embryo is formed in the area pellucida. 2. The epiblast, mesoblast,

and hypoblast. 3. The extension of the blastoderm over the yolk. 4. The
vascular area.

5. The head-fold and the other folds by means of which the
embryonic sac is formed. 6. The outward shape of the embryo. 7. The
formation of the neural tube and alimentary canal: somatopleure and splanch-
nopleure. 8. The amnion. 9. The allantois.

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ERRATUM.

p. 124, in the description of Fig. 39 B, for 'Superior vertebral' substitute

'Jugular.'

LIST OF ILLUSTRATIONS.

FIG.

PAGE

I.

12

2.

DIAGRAMMATIC Section of an Unincubated Fowl's Egg .
A. Yellow yolk-sphere filled with fine granules. B. White yolk-

spheres and spherules of various sizes and presenting different ap

pearances 3. Section of a Blastoderm of a Fowl's Egg at the commencement of

Incubation.

.

15

18

19

4. Section through the Germinal Disc of the ripe Ovarian Ovum of a

Fowl while yet enclosed in its Capsule . 5. Surface Views of the early stages of the Segmentation in a Fowl's

Egg

a

6. Surface View of the Germinal Disc of a Hen's Egg during the later

Stages of Segmentation

23

7. Section of the Germinal Disc of a Fowl during the later Stages of

Segmentation

2+

8. A to N. A series of purely diagrammatic representations introduced

to facilitate the comprehension of the manner in which the body of
the embryo is formed, and of the various relations of the yolk-sac,
amnion and allantois

29–32

33

9. Diagrammatic Longitudinal Section through the Axis of an Embryo.

Section of a Blastoderm at right angles to the long axis of the
Embryo after eight hours' Incubation .

TO.

46

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