CONTENTS 
CHAPTER 
I.—THE LIFE OF THE SIMPLEST ANIMALS . . . . 
The simplest animals, or Protozoa, 1.—The animal cell, 2.— 
What the primitive cell can do, 5.—Ameba, 5.—Parameecium, 9. 
—Vorticella, 12.—Marine Protozoa, 15.—Globigerine and Radio- 
laria, 16—Antiquity of the Protozoa, 20.—The primitive form, 
—The primitive but successful life, 21. 
I].—THE LIFE OF THE SLIGHTLY COMPLEX ANIMALS . r . 
Colonial Protozoa, 24.—Gonium, 25.—Pandorina, 26.—Eudo- 
rina, 27.—Volvox, 28.—Steps toward complexity, 30.—Individual 
or colony, 31.—Sponges, 32.—Polyps, corals, and jelly-fishes, 37. 
—Hydra, 37.—Differentiation of the body cells, 41.—Meduse or 
jelly-tishes, 41.—Corals, 48.—Colonial jelly-fishes, 45.—Increase 
in the degree of complexity, 48. 
TIL—THE MULTIPLICATION OF ANIMALS AND SEX - 3 
All life from life, 50.—Spontaneous generation, 51 _The 
simplest method of multiplication, 53.—Slightly complex methods 
of multiplication, 54.—Differentiation of the reproductive cells, 55. 
—Sex, or male and female, 57.—The object, of sex, 57.—Sex di- 
morphism, 58.—The number of young, 61. 
IV.—FUNCTION AND STRUCTURE . 5 ‘ : . 
Organs and functions, 63.—Differentiation of structure, 64.— 
Anatomy and physiology, 64.—The animal body a machine, 65. 
—The specialization of organs, 66.—The alimentary canal, 66.— 
Stable and variable characteristics of an organ, 73.—Stable and 
variable characteristics of the alimentary canal, 73.—The mutual 
relation of function and structure, 77. 
V.—THE LIFE CYCLE .. : : i 
Birth, growth and dévetuphnat and death, 78.—Life aptiect of 
simplest animals, 78.—The egg, 79. —Enibryonia and post-em- 
bryonic development, 80.—Continuity of development, 88.—De- 
velopment after the gastrula stage, 84.—Divergence of develop- 
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