PLATE 2 



EXPLANATION OF FIGURES 



All of the (Irawiiifrs in this plate were made with the aid of a camera lucida 

 although in most cases, in order to show anything of the curved nature of the X- 

 elements or the full field of chromosomes, the focal plane had to he shifted, so that 

 most of the drawings from fig. 11 to fig. 22 represent composites of two planes of 

 focus. The magnification is in every case approximately 1800 diameters. 



9 First spermatocytes of one of the hybrids showing the prevalent contraction 

 phase at which the maturation process commonly came to a halt. 



10 A stroma cell from the testis of one of the hybrids. 



11, 12, 13, 14 Drawings showing the characteristic U-shape of the X-element 

 of the langshan cock. Figs. 11, 12 and 13 represent division stages of first sper- 

 matocytes. Fig. 14 is from a smear preparation and shows the X-element at the 

 equator of the spindle in a secondaiy spermatocyte ready for division. It divides 

 lengthwise at this time. 



15, 16, 17, 18 Drawings showing the characteristic comma- or pistol-shaped X- 

 element of the guinea. Fig. 17 is viewed from one pole. 



19, 20, 21 , 22, 23 Drawings to show the X-element of the guinea-chicken hybrid, 

 it will be observed that the X-element is of the guinea type. Fig. 20 is viewed 

 from one pole. 



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