CHROMOSOMES IN CAVIA COKAYA. 79 



of parasynapsis. There is no genetic evidence in favor of 

 parasynapsis. 



SUMMARY. 



I. The actively dividing cells are not distributed throughout 

 the whole lining of the seminiferous tubules but are limited to 

 elliptical areas. 2. These areas never exceed two thirds the 

 circumference of the tubules and sometimes consist of only a 

 few cells. 3. The greatest diameter of the ellipse is always 

 lengthwise of the tubule. 4. The areas of actively dividing cells 

 are more numerous and larger in the superactive male. 5. There 

 are thirty-eight spermatogonial chromosomes, which according to 

 size and shape may be grouped into eighteen similar pairs and a 

 pair which is unequal in size which we have designated as the 

 XY-pair. 6. Both the primary and secondary spermatocyte 

 cells have nineteen chromosomes. 7. The XY-tetrad is pre- 

 cocious in its division and the resultant chromosomes are unequal 

 in size. 8. All the chromosomes divide equally in the second 

 division. 9. There is some evidence of parasynapsis. 



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