Fertilization may also be divided into several types based on the number of sperms that enter the egg apart from its classification based on the loca­tion of fertilization as to whether it is internal or external. The following are the various types of fertilization.

1. External fertilization. Fusion in the external media.

2. Internal fertilization. Fusion in the internal media.

3. Monospermic fertilization. Only one sperm enters the egg. This is seen in most of the animals.

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4. Polyspermic fertilization. Here many sperms enter the egg. This of two types-

a. Pathological polyspermy and b. Physiological polyspermy.