Is there a particular reason, medved, that, for this reference alone, you don't provide the year of publication. Could it be that the year -- 1958 -- if given, would make it sound a bit dated? Eh?
The first paragraph of the article, readable here, underscores the datedness when Crow reveals scientific uncertainty as to whether there are 46 or 48 human chromosomes! Equally dated, the article also says that virtually all mutations are harmful, whereas we now know that the vast majority are neutral.
It should also be noted that the article is agenda driven. When you combine the source, Bulletin of Atomic Scientists, with the fact that James F. Crow had pacifist (and possible commie symp) leanings, with the mid/late 50's date (when the United States was still far surpassing the Soviet Union in atomic weapons testing), and read the concluding section of the article, it's clear what is going on. This article has nothing to do with evolution. It's about scaring the American public over the effects of fall-out from atomic testing.