70 THE ASCENT OF THE BODY. 



one can never completely tell. The changes succeed 

 one another with such rapidity that it is impossible 

 at each separate stage, to catch the actual likeness 

 to other embryos. Sometimes a familiar feature sud- 

 denly recalls a form well-known to science, but the 

 likeness fades, and the developing embryo seems to 

 wander among the ghosts of departed types. Long 

 ago these crude ancestral forms were again the high- 

 est animals upon the earth. For a few thousand 

 years they reigned supreme, furthered the universal 

 evolution by a hair-breadth, and passed away. The 

 material dust of their bodies is laid long since in the 

 Palseozoic rocks, but their life and labor are not 

 forgotten. For their gains were handed on to a suc- 

 ceeding race. Transmitted thence through an endless 

 series of descendants, sifted, enriched, accentuated, 

 still dimly recognizable, they re-appeared at last in 

 the physical frame of Man. After the early stages of 

 human development are passed, the transformations 

 become so definite that the features of the contrib- 

 utory animals are almost recognizable. Here, for 

 example, is a stage at which the embryo in its ana- 

 tomical characteristics resembles that of the Vermes 

 or Worms. As yet there is no head, nor neck, nor 

 backbone, nor waist, nor limbs. A roughly cylindri- 

 cal headless trunk — that is all that stands for the 

 future man. One by one the higher Invertebrates are 

 left behind, and then occurs the most remarkable 

 change in the whole life-history. This is the laying 

 down of the line to be occupied by the spinal chord, 

 the presence of which henceforth will determine the 

 place of Man in the Vertebrate sub-kingdom. At this 

 crisis, the eye which sweeps the field of lower NatufQ 



