8 Edmund B. Jf'ilson. 



extent as the white area seen in the living egg; this contains no 

 yolk-spheres, and stains with great intensity with a strong plasma- 

 stain like Congo red. This mass, sharply marked off from 

 the surrounding yolk, bulges slightly outward at the surface and 

 at the margin is continuous with a very thin ectoplasmic zone that 

 entirely surrounds the egg, but is only clearly visible in sections. 

 Internally this mass is confluent with a somewhat narrow zone of 

 similar finely granular protoplasm that extends upwards partly 

 around the germinal vesicle. It is probably to the presence of 

 this remarkable protoplasmic mass that the appearance of the 

 lower white area is due, though the latter may have a different 

 cause. In a general way, the lower protoplasmic area is un- 

 doubtedly comparable with the lower zone, composed of green 

 material, seen in the egg of Myzostoma (Beard, Wheeler, and 

 Driesch), as is proved by its later history. Comparison of my 

 Fig. lo with Wheeler's Fig. 2 ('97), will show how closely 

 similar the relations of the lower protoplasmic area in the two 

 eggs are.^ 



The upper white area cannot be distinguished as such in the 

 fixed eggs, and is apparently produced by a different cause from 

 the lower one. Exactly at the upper pole is a very small, super- 

 ficial disc of clear, dense, intensely staining protoplasm, which, 

 like the lower protoplasmic mass, is continuous at its margin 

 with the general ectoplasmic layer (Fig. 10), This upper 

 disc is so small as readily to escape observation; but suf- 

 ficiently careful examination invariably reveals its presence, which 

 is furthermore frequently indicated by a slight indentation of 

 the egg-periphery at this point. It varies considerably in thick- 

 ness and extent in different specimens, but is always very small 

 at the beginning.^ Evidently, the upper protoplasmic disc is not 

 large enough to account for the appearance of the upper white 

 area in the living egg, which must be due to some other cause. 



1 Compare also Driesch, '96, Fig. 12. 



2 Sfctions of the ovary show that both the upper disc and the lower proto- 

 plasms area are present while the egg is still attached to the ovarian wall. The 

 eggs are greatly distorted in shape, but in a general way are pyriform, and at- 

 tached by the narrow end. The lower protoplasmic area occupies the narrower 

 end, by which the eggs are attached ; the upper disc is at the opposite point. 



