THE ULTIMATE SEX-ELEMENTS. 



8s 



{d) Wolff's Reassertion of Epigenesis. — The above ingenious 

 construction was rudely shaken down, however, in 1759, when 

 Caspar Friedrich Wolff showed, in his doctorial dissertation, the 

 illegitimacy of the suppositions which lay at the root of the 



The first stages of development in a number of animals. A, 

 Sponge, Coral, Earthworm, or Starfish ; B, Crayfish or 

 other Arthropod ; C, Tunicate, Lancelet, S:c. ; D, Frog 

 or other Amphibian. 



I. Fertilised ovum ; 2. Segmented ovum, a ball of cells, morula, 

 or blastosphere ; 3. The same, after further division or in 

 section ; 4. 7"he gastrula stage. 



preformation theory. He traced the chick back to a layer of 

 organised particles (the familiar cells of to-day), in which there 

 was no likeness . of the future embryo, far less adult. More 



