THE PROTOPLASMIC SYSTEM 



basis of an attack by bio-physicists, bio-colloid-chemists, 

 bio-physical chemists, by which may possibly come an 

 elucidation of the problem of vital manifestations. I 

 therefore turn to a description of the cell. 



Under low power of the microscope, a living unfertilized 

 egg of the sea-worm, Platynereis, mounted in a few drops 

 of sea-water, at first glance appears as a greenish-yellow 

 sphere everywhere crowded with smaller spheres except 

 near the centre and at the periphery beneath the well 

 marked egg-membrane; the whole presents a pebbled or 

 shagreen effect. A second glance, especially if the egg is 

 brought into focus so that one obtains an optical section 

 of it, gives clearly the regions first noted. The large clear 

 area near the center is the nucleus, sharply set off from 

 the remainder of the cell by its transparency and apparent 

 homogeneity. Outside of it, closely crowded against the 

 nuclear boundary are innumerable spherules with some 

 twenty or more refringent globules (oil drops) interspersed. 

 Among these spherules and globules minute bright granules 

 are scattered. Under higher magnification still smaller 

 granules may be discerned. Spherules, globules and 

 granules lie in the endoplasm or inner cytoplasmic region. 

 Beyond it is a clear band, the ectoplasm, or outer region of 

 the cytoplasm. In this egg the ectoplasm is crossed by 

 fine radial lines; these appear to reach the egg-membrane, 

 called the vitelline membrane, though actually they end 

 in the plasma-membrane which is difficult to discern and 

 which lies underneath the vitelline membrane. 



If we fix this egg quickly with some chemical reagent 

 which preserves it in a state closely resembling the living, 

 and cut it up into thin slices, we easily discern structures 

 seen with more difficulty in the living cell. Figure i is 

 of a stained slice from such a fixed egg. In the nucleus, 

 granules of various sizes and two chromosomes are shown. 

 These bodies lie In a faintly granular grayish-blue field 



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