It's called the frolis maneuver. it only works with members of the same species (a few humans, for example)...
About frolis maneuvers: I'm pretty sure you can, actually, blend different species if you wanted to, but remember book 35? Where Marco kept doing nasty mixed morphs due to stress? Generally, it's not a good idea.
Even in book 35 though, Marco never stayed in a mixed morph for long. If he had, he would have learned the nasty downside to even some of the more tame mixed morphs that he performed. Let me tell you, mixed morphs have all sorts of health problems if you don't do them exactly right. You get a mismatched circulatory system and have a heart attack, or your lungs don't match up to your airway and you can't breathe. I should know. I'm a mixed morph
nothlit, and let me tell you it took a long time to get all my parts matched up right. Not that it wasn't worth it, but I still don't have depth perception, and my right foot will just randomly hurt sometimes for no reason at all.
Something I've always wondered about. Was the 2 hour limit a technical limitation or a security measure? In #8 Ax mentions that he keeps waiting for Tobias to aks about his knowledge about nothlits, which makes me think that there might some sort answer for the nothlit situation. Also as much as everyone complains about the limit, it was useful too.
I always assumed that the two-hour limit was there because after that, the morph DNA would take over your body. When you're in morph, the DNA is sort of "temporary" with your own, normal DNA hanging out somewhere in the background. But DNA naturally wants to replicate, and DNA that isn't being actively maintained will eventually degrade . . . I dunno, though, it would seem like that would possibly take longer than two hours, though . . .