PLATE 7. 



Fig. 17. a. b. c. Diagrams sho\Yiug escape of larva from egg capsule. 

 X 190. 



Fig. 18. Section of blastula. X 190. 



Fig. 19. Section of gastrula, early stage. X 190. 



Fig. 20. Section of gastrula just before closure of blastopore. X 190. 



Fig. 21. Section of larva immediately succeeding closure of blasto- 

 pore. X 190. 



Fig. 22. Sagittal section of larva at the beginning of two-walled cylin- 

 der stage, showing rapid growth of cells in archenteric wall. X 190. 



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