PLATE 1 
EXPLANATION OF FIGURES 
1 Five-day chick embryo, no. 14. Section through lumbar segment (X 100), 
showing absence both of cerebrospinal nervous system and primordia of sympa- 
thetic trunks and prevertebral plexuses. 
2 Five-day chick embryo, no. 14. Section through anterior lumbar segment 
(X 120), showing remnant of neural tube with small ventral nerve-root (vr), 
but absence of primordia of sympathetic trunks and prevertebral plexuses. 
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