256 PERCY SLADEN TEUST EXPEDITION. 



Fiijs. 13-18. Transverse Sections through a Metamorphosed Animal. 



Fig. 13. Througli braiu and eye-spot. 



Fig. 14. Througli anterior region of buccal cavity, showing Hatschek's pit. 



Fi". 15. Through buccal cavity, near hinder end, showing buccal cirrlii. (For references to numbers, 



see p. 236.) 

 Fi". IG. Through anterior portion of velum and base of buccal skeleton. 

 Fig. 17. Through 1st left gill-slit. 

 Fi"-. 18. Through 15th left gill-slit, sliowing primary gill-bar on the right. The epithelium of the 



epibrauchial and hypobranchial coeloms, and of the coeloniic canal, is omitted. 



