Fig. 21. — Horizontal section of 

 not ni.il troul embryo (PI. I. fig. i). 

 I he se( tion passes through the uppei 

 parts of the eyes, and the auditory 

 organs, as w< II as through the various 

 cavities of the brain, and the i entral 

 anal ol the spinal cord. I ■ 

 with PI. X figs. j9, 40 (union at optic 

 lobes I, M l- fig. 4 ) (union .it medulla), 

 and with PI. XV. fig. 53 (union in 

 pectoral region). For other refen n< es 

 see under PI. 1. lis;. 1. ( ■ 13. 1 



01* 



■ 

 ■ 



Fig. 22.- Horizontal section as 

 above, but passing below the cavities 

 of the optic lobes and the medulla, 

 and cutting through the middle of the 

 eye and the auditory organs. Com- 

 parewith PI XII. figs. 44.45 (union 

 at medulla). Other references under 

 PI. I. fig. 1. (X13.) 



Fig. 23. — Horizontal section as 

 above, but passing through the lower 

 parts of the eyes, brain, and auditory 

 organs, .is well as through the head- 

 kidney, the duct of the swim-bladder, 

 and the dorsal portions of the gill 

 .itches, and of the body cavity. Com- 

 pare with Pis. XL. XII. figs. 42. 45, 

 46 (union at optic lobes, and at 

 medulla). Other references under 

 PI, I. fig. 1. (X13.) 



PL. V. 



