PLATE XVIII. 



Fig. 8. — Section from an individual at the climax of larval life, showing the 

 ectoderm in a region similar to that shown in PI. XVII, Figs. 6 

 and 7. The order with reference to stages represented of 6, 7, 

 and 8. should be 8, 6, and 7, with a considerably greater inter- 

 val between 6 and 7 than between 7 and S. 



Fig. Si. — Section of a larva in the early portion of the third period (metamor- 

 phosis but slightly advanced) to show particularly the coelomic 

 mass, c. in., with its few mesenchyme cells, met:'!/, c, and the 

 character of the cells of the ectoderm, of the mesoblastic 

 pouches, mes. p., ami of the digestive tract. 



Figs. 10, 11. and 12 are from sections of the stomach wall at three distinct 

 larval stages. Ill is of a stage rather late in the first period of 

 larval life, and shows the gastric cells filled with secretion at 

 their outer ends. 11 is from a stomach shortly after metamor- 

 phosis has begun. Here the external secreting ends of the cells 

 have almost though not quite disappeared. 12 is from a larva 

 well advanced in metamorphosis. Here the inner tints of the 

 cells are distinctly secretory, and the nuclei are situated at the 

 outer ends. 



