TEXT FIGURES 



Fig. I. Sea urchin and hedgehog 5 



Fig. 2. Lantern of Aristotle 10 



Fig. 3. Sea urchins in an emblem 12 



Fig. 4. Rondelet's figure of sea urchins 15 



Fig. 5. Sea otter eating sea urchins 25 



Fig. 6. Structure o^ Arbacia test 32 



Fig. 7. Vertical section of ^r^aa'fl 33 



Fig. 8. Young sea urchins in brood pouch of Goniocidaris canali- 



culata 53 



Fig. 9. Membranes and layers of unfertilized egg .... 84 



Fig. 10. Membranes and layers of fertilized egg 84 



Fig. 1 1 . Arbacia spermatozoon 88 



Fig. 12. Breaking of unfertilized egg by centrifugal force . . .124 



