PLATE 1 



EXPLANATION OF FIGURES 



All the figures represent preparations stained with eosin-azure II, and are 

 drawn with the camera, using a B. & L. 1 /12-inch immersion objective with the 

 1-inch eye-piece. 



1 Section through the ventral sinus of a 3.5- to 4-mm. larva. 



2 Head mesenchyme of a 3.5- to 4-mm. larva. 



3 Section through heart wall and cavity of a 5.6- to 6-mm. larva. 



4 Erythrocytes of a 6.5- to 7-mm. larva. 



5 Erythrocytes from the heart of an 8- to 8.5-mm. larva. 



6 Section of the anlage of mesonephros of a 9-mm. larva. 



7 Section through the mesonephros of a 16-mm. larva. 



ABBREVIATIONS 



e.c, eosinophile granulocyte 



e.end., eosinophil endothelium cell 



en.c, endocardium cell 



end., endothelium cell 



Lib., large lymphoblast 



l.lc, large lymphocyte 



l.w.c, lymphoid wandering cell 



m.c, mast cell 



ms., mesenchyme cell 



p.b.c, primitive blood-cell 



p.eb., primitive erythroblast 



p.ec, primitive erythrocyte 



s.c, special cell 



s.lc, small lymphocyte 



sp.c, spindle cell 



w., mesonephric tubule 



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