112 PROCEEDINGS OF THE ACADEMY OF [Feb., 



Fig. 9rt. — Transverse section through the ventral half of the head of 

 an adult brook lamprey, to show the position and relative size of the 

 paired salivary or basilar gland. (Mag. about 17 diam.) 



Fig. 9i.— Transverse section through one side of the salivary or basilar 

 gland and its duct, just anterior to the opening of the latter into the 

 former. (Mag. 50 diam.) 



Fig. 10a. — Transverse section through the ventral half of an adult 

 brook lamprey, cutting through the fourth gill-sacs, to show the position 

 and relative size of the thyroid gland. (Mag. 30 diam.) 



Fig. 10Z>.— Transverse section through the tliyroid at about the plane 

 of the section rei)resented in fig. lOr/. (Mag. 4^0 diam.) 



