Evidence from Metazoan Germ-Cells 



17 



of several species of Ascidians. Among the great merits of 

 this investigation are the facts that the normal living eggs 

 were studied with great care, and that the comparative 

 method was employed to a considerable extent. 



'i.e. 



cru 



g.v. 



C rt. 



v. 



FIGURE 43. DEVELOPMENT OF AX ASCIDIAX EGG (AFTER COXKI.Tx). 



cn., chorion. c.p., clear protoplasm, c.r., crescent of mesoderrnal 



substance, g.v., germinal vesicle, p.b., polar body, p.l., peripheral 



layer of protoplasm, t.c., test cells, y.h., yellow hemisphere of 

 egg- yk., yolk. 



Three species of simple Ascidians, Ciona intestinalis, Mol- 

 gula manliattensis and Styela partita furnished the eggs 

 for the investigations. 



We will begin the examination by quoting from the sum- 



