PLATE XIX. 



Fig. 13. — Shows the secretion of the gastric epithelium being discharged into 

 the eoelomic cavity. 



Figs. 14 and 15 are from sections of the ectoderm of a larva in the climactic 

 period. They are drawn to the same scale and are for the 

 purpose of contrasting the cilia of the ciliary girdle, Fig. 15, 

 with those of the anterior portions of the body, Fig. 14. 



Fig. 16 — Is a diagramatic illustration of the swimming movements of the 

 tomaria. The small circle 10° represents the larva itself, the 

 radiating Hues around the circumference indicating the cilia of 

 the ciliary girdle, and the groupings of different lengths indi- 

 cate the waves. The arrows in this circle show T the direction of 

 travel of the waves. The large circle represents a projection of 

 the spiral described by the larva in its forward progression. 



I21H] 



