21.   On six other occasions, she experienced hormonal changes that resembled those of pregnancy but produced no offspring.

22.   Project organizers hope that the Boston-bred crane chick will follow suit and produce wild offspring of its own when released this fall.

23.   Q. Can the polar bear mate with the brown bear to produce fertile offspring?

24.   Proponents of human reproductive cloning have justified their goals by saying the science could produce offspring for couples who are infertile or have lost a child.

25.   Researchers are planning to use gene technology to stop the fish producing female offspring, forcing the population to crash.

26.   So males and females too genetically alike might have been more likely to produce offspring unable to adapt to their surroundings.

27.   So she is comparing clams in polluted and unpolluted waters to see how many offspring they produce and then incorporating her data into mathematical models that project populations.

28.   Some of the critters were confused by the weightlessness but all appeared healthy, with Japanese red-bellied newts and Medaka fish close to producing offspring.

29.   Some organohlorines mimic the hormone estrogen, thus altering wildlife in ways that diminish their ability and interest in producing offspring.

30.   Stopping frequently, he launched into lengthy accounts of the life stories of the five on display, their frightening moments and especially their occasional triumphs in producing offspring.