Here, the authors characterize two proteins associated with the hexactinellid sponge silica. Retinoic acid signaling is involved in patterning the embryonic antero-posterior axis, and also ...

IN the preliminary account by my friend Prof. Dendy (NATURE, February 7, p. 190) it is difficult to see evidence for the independent organic life of his “scleroplastids”. There is nothing to ...