566 WILLIAM PATTEN. 



stain less deeply^ and are composed of a loose^ apparently 

 granular mass, which, however, on closer inspection, reveals 

 the presence of so many irregular vacuoles as to reduce the 

 yolk substance to a fine network. Such yolk masses are most 

 abundant near the surface. They are probably merely varieties 

 of the first kind, brought about by its gradual absorption to 

 supply food for the rapidly developing germ cells. It is an 

 important characteristic of the yolk that it is not transformed 

 into protoplasm simply by the solution of its outer boundary, 

 as a small block of ice would be dissolved in warm water; on 

 the other hand, the yolk balls do not decrease perceptibly in 

 size, but simply become less dense, and finally are changed 

 into a more or less fine network of deutoplasm, the walls of the 

 yolk ball still retaining its sharply defined outline. It is 

 possible that these cavities in the deutoplasm may have been 

 filled with an oily or fatty substance, which had been dissolved 

 by the reagents used in the preparation of the egg. That a 

 great deal of soluble fatty substance is present in the yolk from 

 the first we have already seen ; but from the configuration of 

 the solid yolk around spaces once filled with fat we can see that 

 a great deal of the substance in question was formed of isolated 

 globules. Since in the very early stages of development the 

 yolk has that homogeneous appearance first described, and the 

 granular yolk only appears after the germinal cells have begun 

 to increase rapidly, the only explanation available is that this 

 transformation of the yolk is brought about either by the 

 gradual absorption of the yolk at many different points in each 

 globule, or the yolk may be first gradually transformed into 

 small fat globules which are then converted into protoplasm, 

 and absorbed by the amoeboid cells. If the eggs had been 

 treated with alcohol and benzole, this fatty substance would 

 have been dissolved, producing the net-like or granular yolk 

 balls just described. It is indeed not easy to decide by which 

 of these processes the yolk is absorbed, since we have no facts 

 at hand which point more plainly towards one conclusion than 

 another. 



If the yolk was decomposed by direct contact with the 



