232 



THE THEORY OF THE GENE 



of the X-chroniosomes frequently gets lost (being caught 

 in the division plane) and this leads to the production of 

 two classes of sperm, with five and six chromosomes. 

 In the maturation of the eggs of the same female the 



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Fig. 136. 

 The two maturation divisions of the egg of Angiostomum nigro- 

 venosum. Six chromosomes are left in the egg nucleus. (After 

 Schleip.) 



twelve chromosomes conjugate, giving six gemini (Fig. 

 136). At the first maturation six go into the first polar 

 body and six remain in the egg. These split and six daugh- 

 ter chromosomes go into the second polar body, leaving 

 six chromosomes in the egg, each with one X-chromo- 

 some. An egg fertilized by a sperm with six chromosomes 



