HOW REPRODUCING CELLE GET TOGETHER 13 
1. What is pollen? 
2. Where is the ovum in flowers? 
3. How does the sperm cell reach the ovum? 
4. How is pollen brought to the pistil? 
5. What is the difference between close fertilization and cross 
fertilization? 
In Water Animals. The process by which the reproducing 
cells are brought together differs a great deal in different 
animals. Some water animals, as barnacles and corals, live 
in colonies fastened to rock or shell foundations. Others, 
as clams and starfish, move about independently but exist in 
large numbers in the same locality. The males of such ani¬ 
mals simply discharge their spermatozoa into the water in 
the season when the eggs are ripe, and rely on some of them 
finding their way to the egg cells. 
Some fish smooth off a place in the sand or find under a 
stump a nook in which the female lays her eggs; then the 
male takes charge of the nest and deposits the milt, which 
consists of millions of spermatozoa. Most of the eggs are 
soon fertilized by the spermatozoa which swarm about. 
Frogs fertilize their eggs in a way very similar to that of the 
fish, but the male frog clings to the female and deposits the 
spermatozoa on the eggs just as they are being laid in the 
water, thus making their fertilization more nearly certain. 
1. What is the common method by which spermatozoa find the 
egg cells of small water animals ? 
2. What do fish and frogs do to make the meeting of the repro¬ 
ducing cells more nearly certain? 
In Land Animals. Obviously the land animals cannot 
discharge their spermatozoa aimlessly with any probability of 
their reaching their goal, the egg cells. They must employ 
another method. In all the higher animals and in many of 
the lower, such as insects, the male introduces the sperma¬ 
tozoa into a sack in the female’s body prepared to receive 
them. This is done in the act of mating. 
