Vm CONTENTS 



8 Sense Organs and Behaviour 79 



1. Sensory equipment 79 



2. Reactions to light 83 



3. Reactions to heat 92 



4. Reactions to mechanical stimulus 94 



5. Reactions to gravity 96 



6. Reactions to chemical substances 97 



9 Reproduction and Development 101 



1. Introduction 101 



2. Fertilization 104 



3. Egg laying and brood care 110 



4. Development of the eggs 116 



5. Embryology of a glossiphoniid leech 121 



6. Embryology of a gnathobdellid leech 127 



7. Special features of piscicolid embryology 130 



8. Phylogenetic considerations 133 



9. Evolutionary history 134 



10 Ecology 136 



1. Relations with the inanimate environment 136 



2. Relations with the animate environment 139 



Appendix A. The Systematics of Freshwater and 



Terrestrial Leeches. By K. H. Mann 147 



Appendix B. The Systematics of Marine Leeches. 169 

 By Professor E. W. Knight-Jones 



Bibliography 187 



Index 197 



