LIST OF ILLUSTRATIONS. 
xix 
FIG. 
PAGK 
90. Fourth Abdominal Segment of Crayfish [5]. 
91. Crayfish Appendages [5]. 
92. Longitudinal Section of Crayfish [5]. 
93. Walking Appendage of Crayfish with Gill Attached [5]. 
94. The Common Crab. 
95. Early Stages of Shore-crab. 
96. Water-flea [2]. 
97. Cyclops [2]. 
98. A Barnacle. 
99. Forms of Amoebae. 
100. Amoeba Feeding [2]. 
ior. Amoeba Dividing [2]. 
102. One of the Foraminifera. 
103. The Origin of Chalk. 
104. Infusorial Earth. 
105. Infusorians. 
106. Vorticella [8]. 
107. A Paramecium [5]. 
108. Structure of a Sponge. 
109. Sponge Spicules [2]. 
no. Thread-cells [2]. 
in. Forms of Hydra [8]. 
112. Hydractinia [6]. 
113. Medusae of Campanularian Hydroid [6]. 
114. The Origin of a Scyphozoan Jelly-fish. 
115. The Structure of a Sea-anemone. 
116. A Starfish. 
117. A Brittle Starfish. 
118. The Structure of a Sea-urchin. 
119. A Sea-cucumber. 
120. An Earthworm. 
121. A Worm’s Setae. 
122. Worm-casts. 
123. A Fresh-water Mussel Showing Position of Foot and Siphons.. 
124. Fresh-water Mussel with One Valve Removed [5]. 
125. Digestive Tube of Fresh-water Mussel [5]. 
126. Cross-section of Anodon [5]. 
127. Nervous System of Anodon [5]. 
128. A Slug. 
129. A Snail. 
130. A Squid. 
131. Part of a Lingual Ribbon. 
132. The Circulation of Blood in a Fish. 
133. Internal Organs of Fish. 
134. Skeleton of a Fish.;. 
135. Tongue of a Frog. 
136. A Young Tadpole Showing External Giils [2]. 
137. Under Side of Tadpole Showing Coiled Intestine and Internal 
Gills [2]. 
138. Heart of Adult Frog [2]. 
139. Blood-cells of a Frog [9]. 
104 
10 5 
106 
107 
108 
108 
109 
109 
no 
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118 
119 
120 
120 
121 
121 
122 
123 
124 
125 
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136 
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157 
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