PLATE 20 



EXPLANATION OF FIGURE 



Fig. 26 Photomicrograph of a transverse section of a twenty-two-day rain- 

 bow trout embryo taken through the anterior end of the left subocular lymph 

 sac (/ ) ; showing that the anterior extension of the sac is brought about by a con- 

 fluence of independent anlagen. P. E. C. 648, slide 1, section 48. 



REFERENCES 



1, Subocular lymph sac 



114 



