Charles R. Stockard. 507 
Fies. 27 to 31. The development of the pouch of the first branchial gill 
x 60 diameters. Fig. 27. gp, portion of the gill tube with its walls bulged 
apart to form a chamber the earliest anlage of the pouch. g, pharynx. The 
gill connection with the pharynx is anterior of this section. Fig. 28. In an 
older embryo, the walls of the chamber beginning to fold. Fig. 29. A still 
older stage the pouch walls further folded. Fig. 30. The pouch increased in 
size and becoming more complex. Fig. 31. The cartilage arch, Ba, is forming 
about the external gill tube; ep, the ectodermal pocket. The pouch is larger 
and more complex than formerly. Fig. 32. Through a gill pouch in the mid- 
branchial region of a lately hatched embryo. g, pharynx; et, section of the 
external gill tube. 
