So, I was trying to remove the Blemished tag from my Slime Boy, got all the things ready, only to find I, in fact, couldnt even select him as a Lab subject. He just isnt listed there. 

Im playing the 0.5.25 version. 

hahahaha, ahh bugs, imagine this is intended, slimes are just less good race than you would like them to be, just because of that

get a cat instead :D , have fun