THE THEORY OE GERMTNAL LOCALIZATION 



299 



independently developing pieces." ^ This conclusion seemed to form 

 a very strong support to His's theory of germinal localization, 

 though, as will appear beyond, Roux transferred this theory to the 

 nucleus, and thus developed it in a very different direction from 

 Lankester or Van Beneden. 



Fig- 131. — Half-embryos of the frog (in transverse section) arising from a blastomere of the 

 2-cell stage after killing the other blastomere. [Roux.] 



A. Half-blastula (dead blastomere on the left). B. Later stage. C. Half-tadpole with one 

 medullary fold and one mesoblast plate; regeneration of the missing (right) half in j^rocess. 



(7A-., archenterio cavity : c.c, cleavage-cavity; cli, notochord ; w./, medullary fold ; wj., meso- 

 blast-plale. 



In an able series of later works Whitman has followed out the sug- 

 gestion made in his paper of 1878, already cited, pointing out how 

 essential a part is played in development by the cytoplasm and insist- 

 ing that cytoplasmic pre-organization must be regarded as a leading 

 factor in the ontogeny. Whitman's interesting and suggestive views 



^ I.e., v>. \o. 



