CONTENTS. 



PAGE. 



I. On the Rhizocephalan genus Thpmpsonia and its Relation to the 



Evolution of the Group. By F. A. POTTS. 2 plates, 



12 text-figures 1-32 



Introduction 3 



Previous Work on Thompsonia 5 



Preliminary Description of Material 7 



The Root System 9 



The Structure of the External Sacs 16 



Development 18 



The Changes in the Visceral Mass during Development 20 



The Liberation of the Cypris Larvae 21 



The Formation of New External Sacs 21 



Development of Germ Cells in the Root System 23 



The Social Forms of Peltogaster and Thompsonia compared 24 



The Evolution of Thompsonia 26 



Thompsonia and Thylacoplethus 27 



Amended Diagnosis of Genus 28 



The Species of Thompsonia 29 



The Influence of the Parasite on the Host 30 



Summary 31 



Bibliography 32 



II. Hapalocarcinus, The Gall-forming Crab, With some notes on the 



Related Genus Cryptochirus. By F. A. POTTS. 3 plates, 



19 text-figures 33-69 



Hapalocarcinus marsupialis Stimpson 35 



Introduction 35 



The Galls in Pocillopora ccespitosa 38 



The Galls in Seriatopora hystrix 41 



Gall formation in Stylophora and Sideropora 44 



Action of Respiratory Current on Individual Polyps 44 



The General Configuration of the Buccal Area 47 



The Buccal Appendages 49 



The Stomach 50 



The Contents of the Stomach 52 



The Female and its Various Stages of Growth 56 



The Male 58 



The Eggs and Larvse 60 



Cryptochirus Heller 61 



A Comparison of Hapalocarcinus and Cryptochirus 64 



The Affinities of the Hapalocarcinidae 67 



The Hosts of Hapalocarcinus and Crypotochirus 68 



Summary 69 



Bibliography 69 



in 



