CONTENTS . 



1. Introduction. X. 



2. Historical Sketch. £• 



3. Distribution and fjfcits. 7. 



4. Physiological Notes. 11 



5. Early Stages. /6, 



G. Stage "A". Origin of Anterior Enterocoels. If, 



7. " "B". " " Hydrocoele XL 



3. " "C" Closing Of the Blastopore and Formation 



of the Mouth. M' 



9. " '^"Rotation of the Hydrocoele completed .- 



10. " "E" .Second Pair Tentacles. 30, 



11. " "F" .Invagination of the Nervous System. — 3?. 



12. " "©".Degeneration in LArval Organ Begun.— ipj t 



13. " "H" .Formation of Subneural Sinus. ^ 



14. Elation of Larva to Adult. 4|T. 



15. Larvae of Antedon and Ophiura Compsr--i . <<>X- 



1C . Literature Cited. •©<<>. 



17. Description of Figures. t /» 



io. Vitt. 13. 



