) The authors claim that Nodal/Vg0 heterodimers mediate Nodal signaling. This statement requires at least direct prove that such heterodimers bind to nodal receptors and, ideally, that they mediate receptor activation. This could be shown by IP experiments showing binding of both Cyc and Vg0 to phosphorylated Nodal receptors.  We thank the reviewer for this suggestion. Please see our last response to point 0 above.  > 0\) The authors show that Vg0 binds to Cyc and Sqt in vivo by colocalization of tagged versions of these ligands in the extracellular space ([Figure 0](#fig0){ref-type="fig"}). These colocalizations should be quantified to show what fraction of extracellular Vg0 is bound to Nodal ligands and vice-versa.  