PLATE 1 



EXPLANATION OF FIGURES 



17 Left lateral view of a wax reconstruction of the pharynx of an Acanthias 

 embryo 5 mm. long (No. 6). E.l and E.2, ectodermal plates of the first and 

 second gill clefts, respectively. These plates are cut away arbitrarily around 

 their edges. G.P. 3, third gill pouch which has not yet fused with the ectoderm; 

 Nc, notochord; O.Pl., oral plate; T., thyreoid. X 75. 



18 Right lateral view of a wax reconstruction of the pharyngeal floor of an 

 Acanthias embryo 14 mm. long (No. 24). G.P.I and G.P2, first and second gill 

 pouches, respectively; O.PL, oral plate; T., thyreoid. X 100. 



19 Ventral view of a wax reconstruction of the thyreoid gland of an Acanthias 

 embryo 21 mm. long (No. 34). X 100. 



20 Ventral view of a wax reconstruction of the thyreoid gland of an Acanthias 

 embryo 24 mm. long (No. 36). X 100. 



21 Ventral view of a wax reconstruction of the thyreoid gland of an Acanthias 

 embryo 28 mm. long (No. 38). X 100. 



In figures 20, 21, and 22 the dark areas represent the position of intraglandular 

 cavities whose outlines have been projected on the ventral surface of the gland. 



220 



