\ 



a 



6 



?5^.# 



d 



PLATE II. Development of a single embryo from two fused eggs. Crosswise 

 fusion (a) of two newt eggs at the 2-cell stage results in the production of 

 a single embryo (b), the four quadrants of which arise fi'om one or the 

 other of the original eggs altei-nately. (c). Even eggs of different species 

 (Triton taeniatus and T. alpestris), fused in this way, may produce a single 

 embryo (d). After Mangold and Seidel. 



