CONTENTS. 



Page 



I. Introduction l 



II. General description of the external form : 



(Physiognomy) 4 



III. Special description of the organs: 



(Organology) 8 



1. Ike skeleton system 8 



a. The ambulacral skeleton of the arms 8 



b. The ambulacral skeleton of the disc 11 



2. The cuticular system 16 



a. The dorsal integument 16 



b. The ventral integument 16 



c. The calcareous parts belonging to the integument 17 



O- The interior calcareous elements of the skin 17 



p. The spines 18 



f. The pedicellarise 21 



3. TJie water system 23 



a. The ambulacral vessels 23 



b. The water-feet and their ampullse 24 



c. The madreporic body and the stone-canal 24 



4. The muscular system 25 



5. The nervous system 26 



6. Organs of sense 26 



7. The digestive system 28 



a. The bucal aperture with its muscular apparatus (the bucal membrane) . . 28 



b The digestive cavity 29 



c. The radial caaca 30 



8. The perivisceral cavity (cceloma) and the blood-system 31 



9. Organs of secretion 34 



10. Organs of generation 35 



a. The ovaries 35 



b. The spermaries (testes) 36 



IV. General arrangement of the various organic systems: 



{Topography) 38 



V. The vital functions: 



{Physiology) 41 



1. The animal functions 41 



A. Movement 41 



B. Sensation 43 



C. Functions of the pedicellaries 44 



2. The vegetative functions 46 



A. Nutrition 46 



a. Reception of food 46 



b. Digestion 47 



c. Circulation of the blood 47 



d. Respiration 49 



e. Secretion 50 



GO 



