"Splice" has the DNA of a really great philosophical horror/science-fiction movie, but in the less-than-fully formed thing that was delivered to theaters, some of its most promising traits remain recessive, under-developed.
You may notice the first sign of this gestational glitch in the otherwise wonderfully gooey in vitro credits sequence, where the title and the names of the lead actors are spelled out in mutant organic forms, like veins bulging beneath the surface of fetal skin. The credits read: "Screenplay by Vincenzo Natali & Antoinette Terry Bryant and Doug Taylor" -- which indicates that director Natali worked on it with Bryant, and Taylor was probably either the original writer or did enough of a re-write to merit a screen credit. Someone -- or something -- almost certainly re-formed the last half-hour of the movie, when it suddenly dies and comes back as the predictable horror clone into which it had successfully avoided mutating up until that point.
You can almost feel the splice at which the erratically paced, action-packed ending to another, lesser scary movie has been grafted onto the genetic horror of this one. It happens right around the time Sarah Polley says something like "What's happening?" and Adrien Brody (off-screen, looped dialogue?) says, "I don't know. But she's dying." Thank you, Dr. Exposition.