THE ULTIMATE SEX-ELEMENTS. 



85 



{d) Wolff'' s Reasse7-tion of Epigenesis. — The above ingenious 

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

 Caspar Friedrich \V' olff showed, in his doctorial dissertation, the 

 illegitimacy of the suppositions which lay at the root of the 



. f ~ , 



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

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

 other Arthropod ; L\ Tunicate, Lancelet, &c. ; /?, Frog 

 or other Amphibian. 



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

 or blastosphere ; 3. 'I'he same, after further division or in 

 section ; 4. J 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 



