56 



COELENTERATA 



7 4 S 





12 



[CH. 



FIG. 20. Section through the body-wall of Hydra fusca. Highly magnified. 



After Schneider. 



1. Ectoderm. 2. Endoderm. 3. Mesogloea or structureless lamella. 



4. Nematocyst. 5. Cnidocil. 6. Muscle-fibres of ectoderm cells 



cut acrocs. 7. Nucleus of ectoderm cell. 8. Interstitial cells. 



9. Cuticle. 10. Pigment granule. 11. Food granule. 12. Nucleus 

 of endoderrn cell. 13. Flagelluin. 14. Water vacuole. 



FIG. 21. Preparation of part of the body-wall of Hydra to show the nerve-cells. 

 (After Hadzi.) The endoderm cells are omitted. 



1. Nerve-cell. 



2. Nucleus of ectoderm cell. 

 4. Small cnidoblast. 



3. Large cuidoblast. 



