CONTENTS. 



PAGE 



Introduction 



I. Tropiomelra carinata 2 



1. Cleavage; formation of the gastrula; first 6 hours 6 



2. Formation of the ccelomic vesicle; sixth to twelfth hours 9 



3. Vestibulary invagination; further specialization of the coelom and hydrocccl; 16 to 40 hours 11 



4. Closing of the vestibulum; fixation of the larva 13 



5. The Pentacrinoid stage 17 



6. The development of the skeleton; the Pentacrinoid 20 



II. Compsometra serrata 23 



1. The embryos 24 



2. The Pentacrinoids 26 



III. Isometra vivipara 31 



1. Cleavage; formation of entoderm ' 31 



2. Formation of enterocoel and hydroeoel 34 



3. The differentiation of the larva 36 



4. The fully formed larva 37 



5. The Pentacrinoid stage 41 



6. Development of the skeleton ; the Pentacrinoid 46 



IV. Notocrinus virilis 49 



V. Florometra serratissima 54 



VI. Thaumatometra nutrix 57 



VI. General Part 59 



1. Deposition of the eggs 59 



2. The cleavage 61 



3. The formation of the entoderm; the gastrula 62 



4. The enterocoel 63 



5. The hydroccel 64 



6. The entoderm ; histolysis 67 



7. The primary gonad 68 



8. The ectoderm; larval nervous system 69 



9. The shape of the larva; vibratile bands; vestibulum 70 



10. The skeleton 72 



Explanation of plates 83 



in 



/ t, 



