CONTENTS. 



Page 



I. Introduction i 



II. General description of the external form: 



(Fhysiognonui) 4 



III. Special description of the organs: 



(Organolofiy) 8 



1. Ihe skeleton system 8 



a. The <ambulacral skeleton of the arms 8 



b. The ambulacral skeleton of the disc 11 



2. The citticiilar system 16 



a. The dorsal integument 16 



b. The ventral integument 16 



c. The calcareous parts belonging to the integument 17 



Ot. The interior calcareous elements of the skin 17 



p. The spines 18 



y. The pedicellarisB 21 



3. The water system 23 



a. The ambulacral vessels 23 



b. The water-feet and their ampullae 24 



c. The madreporic body and the stone-caual 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 diprestive cavity 29 



c. The radial cseca 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 



