22 J. BRONTE GATENBY 



that such takes place in Ascidians and Molluscs is now quite 

 certain, but the egg of Saccocirrus does not provide such clear 

 opportunity for study as that of Limnaea or Ascidians. 

 Nevertheless, 1 believe that I have made sufficiently clear 

 observations on a large amount of material to justify the above 

 interpretations. It is only after the dispersal and breaking 

 up of the Golgi body that true fatty yolk puts in an appear- 

 ance, and in many cases it seems that Golgi elements can be 

 traced stop by step as the eggs grow, metamorphosing into 

 fatty yolk. The extruded nucleolar material has nothing to 

 do with this, and I do not think that the mitochondria are 

 concerned in the process. 



When we take the case of extruded nucleolar material in 

 Saccocirrus it is difficult to understand why the bulk of the 

 formed reserve granules in the egg should be of nucleolar 

 origin. If one studies the cytoplasm of the egg in a number 

 of different examples of oogenesis, one sometimes finds that the 

 nucleolus supplies the bulk of reserve material (Saccocirrus), 

 sometimes the Golgi apparatus (Patella or Limnaea), some- 

 times the mitochondria, as in certain insects. In each of these 

 cases, however, analysis of the entire reserve materials in the 

 egg cytoplasm leads one to a similar conclusion for each 

 example, namely, that reserve material in eggs of invertebrates 

 consists of protein and fat or lipin (or both these). Then, of 

 course, most eggs contain glycogen. 



In some examples, as in the sponge Grautia, the main bulk 

 of reserve material seems to be delicate vacuoles of lipin 

 originating from the ground plasma. 



(b) The Preciseness of the Modern Technique 

 for the Cytoplasmic Inclusions and for 

 Chromatin. 

 Some observers apparently unacquainted with the finer 

 usages of modern cytological technique have wTitten doubt- 

 fully of the preciseness of such methods. In all the cyto- 

 logical problems that I have attacked the difficulty I have 

 met with lies not especially in the discrimination between 

 yolk, Golgi elements, mitochondria, nucleolar deutoplasm, and 



