PLATE 21 



EXPLANATION OF FIGURES 



Fig. 27 Photomicrograph of a transverse section of a sixteen-day steelhead 

 trout embryo, taken through an independent anlage (3') of the lateral pharyngeal 

 lymphatic, at about the level of the first efferent aortic arches; compare 8' in 

 figures 5 and 27. P. E. C. 751, slide, 1, section 91; injected embryo. 



Fig. 28 Photomicrograph of a transverse section of a seventeen-day steel- 

 head trout embryo, taken through independent anlagen (,?') of the lateral pharyn- 

 geal lymphatic, at about the level of the first efferent aortic arches ; compare S' 

 in figures 6, 7 and 28. P. E. C. 740, slide 1, section 103; injected embryo. 



REFERENCES 



3', Independent anlagen of the lateral 15, Hyoidean artery 



pharyngeal lymphatic which lie an- 16, First efferent aortic arch 



terior to the otic communication 27, Root of dorsal aorta 



0, Precardinal or jugular vein 



116 



