I ended up using Gorilla Super Glue GEL on the crack. Now that it has set, it seems that this repair might have caused problems if the crack had fallen on a part of the saddle that gets sat on; however, given that the crack is at the rear of the saddle (I know...I am grinning at the juvenile "crack" and "rear" references, too, but I couldn't think of other words to use!) I think it's going to be OK. The gel seems to have put the brakes ('like THAT one?) on any further spreading of the damage. We'll see.