The Twenty-Five Embryos by Sam Prien

Doctor Robert Casa was just your typical college professor at a university in the western part of Texas; working on research, trying to teach disinterested students and ignoring what he considered stupid university rules. Until that fateful day his university loaned him out to help out a local sheriff at an accident scene because of his special skill in handling human embryos. Little did Casa know that a summer drive to look at an accident in the desert would lead to a series of adventures with the fate of mankind, not to mention his own life, constantly hanging in the balance.