112 CHROMOSOMES DURING SYNGAMY IN PROTOZOA 



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bb' 





cc G 





Fig. 66. — Chromosomes of Aggregate eberthi ( x 2,000). (After Dobell 

 AND Jameson, 1915.) 



A . Nucleus of male, showing six long chromosomes at prophase stage of first division . 



B. Later stage of first division of nucleus of male: the chromosomes have become compact and 



are arranged as an equatorial plate. 



C. Later stage: each chromosome has divided to give rise to two groups of six daughter chromo- 



somes. 



D. One of the groups of six dumlitcr cliroinnsonics arisiim from first division of male nucleus 



elongating to form the chroinnsdiiics of one of tlio dauuhtcr nuc-k'i. 



E. Nucleus of female before fertilization, sliow ini: six limu chromosomes. 



F. Chromosomes in zygote nucleus: early sta^c of first division, showing twelve chromosomes, 



six (a-/) derived from the male, and six (■'-/') fnun the female. 



G. Chromosomes in zygote nuolens: equatorial ])late stage of first division: the twelve chromo- 



somes have contracted and Ixcome associated as six double chromosomes. 

 H. Chromosomes in dividinu zyt:ote nucleus: the individual chromo,somes of each pair have 



separated, giving rise to two groups of six. 

 K. End of first division of the zygote nucleus : one of the groups of .six chromosomes, which have 



elongated, entering the daughter nucleus. 

 L. Group of six daughter chromosomes on sjiindJe of a later nuclear division of the zygote. 

 M. Group of six chromosomes forming equatorial plate at second division of the spore 



nucleus. 



