Sounds like your horse is def. A cryptorchid. Get him gelded, and soon. I went through this with one of our foals, who started getting really fiesty at 15months old. We didn't even know he was a crypt. Stallions can regulate the temperature of their testes when they are "down" in the sack. When their teste is retained, they are unable to regulate the temperature and it can cause their hormones to go out of control. They can become dangerous. (explained by my vet, who I later worked for) Never consider a crypt. Stallion for breeding, as it is passed on by the stallion, not the mare, same with hernias.