VUl CONTENTS. 



gastrula — the Phagocytella, 107. Balfour's views, 108. The gastreea 

 theory, 108. MetschnikofF's misunderstanding of Balfour's views, 109. 

 Reasons against regarding the hollow blastu.la as representing a primitive 

 form, 110. Hypothesis that the primitive form was solid, 111. Argu- 

 ments from Sponges, etc., 112. Haliphysema, 113. The mesoderm, 114. 

 Hypothesis as to origin of the Triploblastica, 115. Primitive streak a 

 growing point; structure of primitive streak, 116. The characters of the 

 ccclom and vascular space, 117. Body cavity of Arthropoda not ccElomic, 

 117. Coclom of Arthropoda, 118. Nephridia of Arthropoda, &c., 

 Grobben, Lankester, 119. Ooelom of MoUusca, 120. The cases of the 

 Nemertinea and Hirudinea, 121. Summary of the development of the 

 coelom and vascular space, 122. 



CHAPTER VI. 



The changes from stage G to Birth, pp. 125 — 144. 



The ectoderm, 125. The ventral organs, 126. The nervous system, 

 128. The eyes, 129. The ventral cords and nerves, 130. Continuity 

 in origin of muscles, nerves and fibrous matter of central nervous sys- 

 tem, 130. Slime glands and crural glands, 132. The endoderm, 132. 

 The muscles, 133. The body cavity and vascular system, 134. The 

 nephridia, 137. The generative organs, 140. The nephridia as direct 

 differentiations of the coelom, 143. 



Bibliography, p. 144. 

 Description of Plates. 



