A current and laudable trend in the teaching of biology is to adopt a horse's mouth approach, letting the innovators speak for themselves. So many are articulate, so many aware of the shortcomings of method and of the difference between speculation and experimental evidence that the lesson is obvious. So Elof Axel Carlson of the University of California at Los Angeles has edited a collection of documents to introduce modern biology to the student. On the whole his choices are excellent, granting that his bias is the bias of the last emphasis on genetics and biochemistry. Here is Darwin's letter to Asa Gray, Mendel's self-effacing remarks to Carl Nageli; here is T. H. Morgan's long and insightful discourse on the nature of genes and infective organisms, as well as Francis Crick's literate and urbane comments on protein synthesis and the genetic code. How well such a collection serves the general reader without a professor to referee his questions is another matter. There are times when the concise introduction and notes leave gaps, when the vocabulary used, or the organisms discussed, may leave the reader floundering. However there are many general essays that do illuminate. There is much pleasure in reading the original words and noting how early or recently they were written. This chronological historical approach points to the dynamism of science. At no time is the ""truth"" complete. Controversies arise to be decided later, or to be left still hanging. This makes even more impressive the words of those individuals who grasped certain principles long before the tools were available to establish their correctness.