Evidence from Metazoan Germ-Cells 



17 



of several species of Ascidians. Ainonfr the great merits of 

 this investigation arc the facts that the normal living eggs 

 were studied with great care, and that the comparative 

 method was employed to a considerahle extent. 



ca. 



c rt. 



FiGURK 4:^. i)i:vp:r,op,^tKNT OF AX AsciDi.xN viAi (afikk coxki.ix). 



en., chorion, c.p., clear jirotoplasni. c.r.. crescent of niesodcrMial 



suh.stance. jLi'.N'., ^x'rniinal Ncsiclc. |).l>., polar- l)o<l\ . p. I., jx-riplicral 



layer of ])rotopla.sni. t.e., test cells. \ .li., yellow luMnisj)licrc of 

 egg. yk., yolk. 



Three species of simple Ascidians, Ciona intestifuiUs, Mol- 

 gula manhattensis and Siyela partita furnished the ^'^^i:,^ 

 for the investigations. 



We will begin the examination by quoting from the sum- 



