The Origin of Specific Proteins 105 



an arginine-rich histone and later, in the sperm, hy protamine. After 

 fertilization, the protamine of sperm chromosomes disappears and 

 is replaced by faintly basic histones which differ from adult histones 

 in their inability to bind fast green, and from protamines, both by 

 their inability to bind eosin and also by their weakly positive reaction 



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f-jfc, km in 



*&&?. 



FIG. 4. Electron micrograph of "pigmented" retina of Swiss albino mouse, 15 days 

 post partum. Fixed in osmic acid embedded in EPON-812, stained with uranyl ace- 

 tate. Note the two nonpigmented melanosomes arrested at successive stages in 

 development. No pigmentation of these melanosomes in albinos has been observed. 

 (Courtesy of Dr. Frank H. Mover.) 



with bromphenol blue. These "cleavage" histones are found in both 

 the male and female pronuclei, the early polar body chromosomes, 

 and the nuclei of the cleaving egg and morula stages. During gast Fil- 

 iation the histone becomes indistinguishable from that of adult 

 somatic cells. Before gastrulation much evidence suggests that the 

 chromosomes are nonfunctional (Moore, 1955; Briggs et al., 1951). 



