116 



CHARLES R. STOCKARD 





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Fig. 5 Camera lucida outline of the tail end and caudal yolk region of an 

 embryo 48 hours old, fixed and cleared in glycerine-formalin. The germ ring 

 just closing over the yolk pole, numerous mesenchjine cells beginning to wander 

 away from the caudal end, huge periblast nuclei indicated in outline and stipple 

 over yolk. Yk, polar bit of yolk just being covered by union of germ-ring border. 



Fig. 6 Portion of the caudal half of an embryo of 48 hours showing the first 

 two pairs of somites recently formed, cells of the lateral plate mesoderm extend 

 out upon the yolk as shown in outline, some beginning to wander away. Peri- 

 blast nuclei outlined and stippled. Glycerine-formalin specimen. ' 



