1839 (Royal Soc.) 129 327 Authors on the ovum of the Bird describe their ‘primitive trace’ of the embryo as originating in that which has been denominated the ‘central, thickened part of the germinal membrane’.
1928 C. S. Whitehead & C. A. Hoff (new ed.) i. iv. 155 In its centre is a delicate line or furrow running longitudinally from front to rear, which is called the primitive trace.