EXTRACT XXI. B. 



ON THE DEVELOPMENTAL EVOLUTION OF THE 

 HUMAN ORGANISM. 



EVOLUTION is now generally adopted, as the best working 

 theory in science building, so to speak, and the line of 

 progress, to which all advances of truth and all tentative 

 attempts at systemising knowledge should conform, in 



FIG. 88. FIG. 89. 



FlG. 88. OVUM OF THE RABBIT FROM THE FALLOPIAN TUBE, TWELVE 

 HOURS AFTER IMPREGNATION. (From Bischoff.) 



In the zona a, spermatozoa are seen ; b, two hyaline globules or polar bodies within 

 the cavity left by the shrinking of the yolk. 



FIG. 89. FRONT AND SIDE VIEWS OF AN EARLY HUMAN OVUM FOUR 

 TIMES THE NATURAL SIZE. (From Reichert.) 



This ovum is supposed to be of thirteen days after impregnation. The surface bare 

 of villi is that next the wall of the uterus, showing at e, the opacity produced by 

 the thickened embryonic disc. The villi covered chiefly the marginal parts of 

 the surface. 



order, that overlappings, and shortcomings, of related 

 truths, may be obviated, on the one hand, and " made 

 good," on the other. 



Regarding evolution, from this point of view, as an 

 instrument of scientific progress, we would seek to take 



