been done on bat vision ( http://www.ncbi.nlm.nih.gov/pubmed/14660703 ), digits , and wing (and http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1622783 ). Furthermore, research has been done on the evolution of the eye , blood-clotting system (per Ken Miller and others), dinosaur to bird digits , and signaling molecules called hedgehog ( http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1000 146). Some of this is