[Advances in Genetics] Volume 15 || X-Autosome Translocations in The Mouse: Total Inactivation Versus Partial Inactivation Of The X Chromosome**Professor Ernst Wolfgang Caspari was 60 years old on October 24, 1969. This work is dedicated to him with the greatest affection and admiration. It is a great honor and privilege to have had him as my mentor.††The unpublished research reported herein and the writing of this review were supported by U.S. Atomic Energy Commission Contract AT (30–1)–2902.