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If there are an odd number of chromosomes, 2N-1, in all the gametocytes of the male, as stated in most accounts of the subject, then if one chromosome fails to divide in the homotypic division, we shall have 2N-2 in one spermatocyte and 2N-1 in the other.
The number then in an egg which develops into a male is 2N-1, while other eggs undergo complete reduction and then have N chromosomes. The latter, however, do not develop until they have been fertilised. In the males, when mature, reduction takes place in the gametes, so that two kinds of sperms are formed, those with N chromosomes and those with N-l chromosomes.
On fertilisation two kinds of zygotes are formed, female-producing eggs with 2N chromosomes, and male-producing eggs with 2N-1 or 2N-2 chromosomes.
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