Two of a kind.

DIRECTIONS: First, read "Together Forever?" (p. 14). Then, solve the clues below to complete this crossword puzzle. To spell out the bonus words, unscramble the letters in parentheses.

ACROSS

1. An--()--is an egg, or female sex cell.

2. --()--twins are twins who are physically connected.

3. An--is a developing young.

4. Male sex cell:--()

5. A--()--is a fertilized egg.

DOWN

6. A--()--()--is an image created by high-energy X-rays.

7. Identical twins are also called ()--() twins.

8. To grow replacement tissue:--()--()

9. Identical twins are the same sex and are ()--()--similar.

10. Fraternal twins are also called--() twins.

Bonus:

a. In 1689, a--physician named G. Konig performed the first known successful operation to separate a pair of conjoined twins.

b. The earliest known pair of conjoined twins was born in 945 in--in Eastern Europe. The twin boys did not survive a surgical attempt to separate them.

ANSWERS

1. ovum 2. conjoined 3. embryo 4. sperm 5. zygote 6. radiograph 7. monozygotic 8. regenerate 9. genetically 10. dizygotic 

Bonus: a. German b. Armenia