CONTENTS 



Chapter Nine: The Main Lines of Evolution Among Land Plants 111 



The Bryophytes 111 



Life Cycle of a Moss 112 



Phylogeny of the Bryophytes 113 

 Origin of the Vascular Plants 113 



Subphyhnn Psilopsida 114 



Subphyhnn Lycopsida 117 



Siibphyhim Sphenopsida 118 

 Subphylum Pteropsida 120 



Ferns 120 



Gymnosperms 121 



The Flowering Plants 122 

 The Main Lines of Plant Evolution 124 

 References 127 



Chapter Ten: The Main Lines of Animal Evolution 128 



Diversification of the Protozoa 128 



Anieba and Its Allies 129 



Ciliata and Suctoria 131 

 Origin of the Metazoa 132 



Phylum P or if era 133 



The Gastrea Theory 134 



Phylum Mesozoa 135 



Phylum Coelenterata 136 



Phylum Ctenophora 137 

 Primitive Bilateral Phyla 137 

 The Protostomous Phyla 140 



Phylum Mollusca 141 



Phylum Annelida 142 



Phylum Arthropoda 143 



The Onychophora—A 'Unique Evolutionary Link 146 



Minor Protostomes 147 

 The Deuterostomous Phyla 148 



Phylum Chaetognatha 149 



Phylum Pogonophora 149 



Phylum Echinodermata 149 



Phylum Hemichordata and the Origin of the Chordata 149 

 Some Evolutionary Generalizations 151 



Origin of New Groups from Primitive Ancestors 151 



Rates of Evolution 152 



Trends in Size 153 



Complexity and Efficiency 153 



Dollo's Law 153 



The Significance of Extinction 154 

 References 154 



Chapter Eleven: The Phylum Chordata 155 



Theories of Chordate Origin 155 



The Nemertean Theory 155 



The Arachnid Theory 155 



The Annelid Theory 156 



The Echinoderm Theory 157 

 Major Divisions of the Phylum Chordata 157 

 Superclass Pisces 159 



Class Agnatha 159 



Class Placodermi 159 



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