244 WILSON. 
DESCRIPTION OF PLATE III. 
Fic. 11. Trans. sec., through lowest part of cesophagus, of a larva in which the 
cesophagus along its whole length is apposed to the surface ectoderm. D, 4. 
Fic. 12. Long. sec. of larva at about the same stage as Fig. 11 in the plane of the 
first two mesenteries. D, 4. 
Fic. 12’. Median long. sec. of a larva, in which the cesophagus is applied to the 
surface ectoderm along the lines of the first and second mesenteries. An older stage 
than Fig. 12. D, 4. 
Fic. 13. A section to one side of Fig. 12, through future intermesenteric cham- 
bers:, (D) 4. 
Fics. 14, 15, 16,17. Series of transverse sections, numbered from above down 
(Fig. 14 is through the cesophagus), from a larva in which the first pair of filaments 
and the first mesenteric ridge are present. Along the line of mesentery 2, the cesoph- 
agus is still applied to the surface ectoderm. D, 4. 
Fics. 18, 18@. Trans. sec., through cesophagus, of a larva with two complete 
mesenteries and a pair of filaments. Fig. 18 @ is the upper of the two. D., 4. 
Fic. 19. Surface view of balsam preparation. The larva has two long, and one 
(possibly two) short filaments. C, 2. 
