THE FLAMINGO'S SMILE; Reflections in Natural History. By Stephen Jay Gould. W.W. Norton. 476 pp. $17.95.

I BELIEVE that if someone were to read me any three sentences from a random essay by Stephen Jay Gould I could identify the author. This is partly because I have read nearly everything that Gould has written for popular consumption during the last decade, but it is mostly because, along with a few writers on science such as Lewis Thomas and John McPhee, Gould has developed -- he probably always had -- a very particular voice.

In the first place, his writing never strays very far away from his fields of special competence -- paleontology, biology and geology. One will never find a Gould essay on, for example, the theory of elementary particles. (I wish some of my physicist colleagues would exercise the same restraint when they, for example, attempt to apply the most naive quantum mechanics to a biological system like the human brain).

In the second place almost all of his essays begin with some odd particular fact, e.g., the fact that when a flamingo feeds, it appears to smile. That is because it turns its head upside down to eat and its mouth is above its eyes. This odd fact, Gould then shows, fits into a large and important general law; the flamingo's inverted behavior has associated with it a whole set of evolutionary inversions. The flamingo's lower jaw has evolved to behave like a "normal" bird's upper jaw; a fascinating example of Darwinian adaption.

Finally, Gould's essays, even the most technical of them, have to do with the splendor of life in all its multifoliate forms -- a subject that could occupy a lifetime.

His latest collection -- his best and richest collection of essays -- is, in fact, entitled The Flamingo's Smile. All the aspects of the Gould voice are on display here. Those of us familiar with the Gould opus know that he is something of a baseball nut. In these essays he has managed to include one in which he offers a novel explanation of why there are no more .400 hitters. This has to do with the "professionalization" of the game. Both the lowest and the highest batting averages are moving closer to the mean because every aspect of the game has gotten better. Gould sees in this an analogy to the evolution of life forms. When certain new life forms are introduced they vary in all sorts of ways. They experiment in the production of what used to be called "sports," or mutants. Most of these experiments fail and the species evolves towards some sort of viable mean. As Gould writes, "When systems first arise, they probe the limits of possibility. Many variations don't work; the best solutions emerge, and variation diminishes. As systems regularize, their variation decreases." No more Ted Williamses.

If I have a cavil about this collection it is an editorial and generic one. These essays all first appeared as columns in Natural History Magazine. Having done such books myself, I am all in favor of essays that have appeared over a span of several years in one or more magazines being collected and housed between hard covers. This is a service to the reader as well as a pleasure for the writer. However, it does pose problems. One of the problems has to do with the possibility that once having written something, one might decide that it was either wrong or badly expressed. What to do from the point of view of a collection? Two solutions are possible; the first is to add postscripts and the second is to simply rewrite the essay. The latter is probably the correct thing to do. If not, one runs the risk of producing something like Douglas Hofstadter's Metamagical Themas which has been rendered all but unreadable by piling postscript on postscript, outweighing and often contradicting the original essays.

Surely, no one who reads a collection of essays like Gould's or Hofstadter's really cares if an essay in the book deviates from the original. What one cares about is the final product, which should represent the best thinking and writing the author is capable of when the book itself is being written. Happily, Gould, unlike Hofstadter, uses postscripting relatively sparingly. There are a few unnecessary repetitions of both phrases and identifications in the book, which could easily have been removed, but they do not spoil the pleasure of reading these wonderful essays.

As Gould tells us in the preface of his book, he has, for the last few years, been fighting a deadly form of cancer. Nothing in these essays shows any trace of this struggle. Rather, they show the joy and wonder of our world. I look forward, and for a long time to come, to reading more essays by Stephen Gould.