FIG. in. Section through head of a semi-cyclopic 

 trout embryo, from same series as PI. XXV. figs. 109, 

 no, but further back in the series. The section passes 

 almost horizontally along the trabeculae cranii, which 

 here form a. single mesial rod. See pp. 40, 44. 

 Anteriorly, the trabeculae are seen to articulate with 

 the palato-pterygoids ; behind them the two external 

 recti of the eye are passing through the pituitary 

 space in company with the two choroidal arteries. 

 The head is somewhat compressed in the sagittal 

 plane. (x24.) 



I-'IG. 113. Transverse section of body 

 of trout embryo just behind the pectoral 

 tins, showing local absence of the noto- 

 chord. The adjacent neural and haemal 

 aid) cartilages fuse together to form a 

 series of half rings below the spinal cord. 

 The lateral muscles meet in a mesial 

 raphe above the dorsal aorta and below 

 the spinal cord. See p. 54. ( x 20. ) 



' 



FIG. 112. Transverse section through 

 atrophic head of an embryo trout, in 

 w hich the lenses alone of all the eye struc- 

 tures have survived. Even the mouth, 

 the Meckel's cartilages, the trabeculae, 

 and the palato-pterygoids are absent. 

 See pp. 60, 61. ( x 16.) 



FIG. 114. Transverse section of double monster belonging to the type 

 described under Class V. on pp. 20-21. The section passes across the 

 middle of the body, and shows the twin sets of structures coming together to 

 unite in lateral union. The intestinal canals are here separate, as also 

 are the livers, air-sacs, Wolfh'an bodies, etc. ( x 16. ) 



PL. XXVI. 



