240 Chas. W. and G. T. Hargitt. 



and the great amount of chromatin present, which does not take 

 part in the formation of the definitive chromosomes, are points 

 of considerable interest and significance, but are probably incap- 

 able of complete explanation in the present state of our knowledge. 

 But may not a partial explanation possibly rest on the ground of 

 a physiological need during the growth period, as earlier indicated 

 by Wilson (1900, p. 128) when metabolism is extremely active, 

 in the elaborating of reserve food material which shall furnish the 

 energy for the following cell divisions and for growth? When the 

 growth period is completed and the reserve food formed a con- 

 siderable portion of the nuclear substance, now unnecessary, is 

 cast aside, just how is of little importance. 



The history of the nucleolus during the growth period contains 

 some points of interest. This body in young oocytes stains red 

 in hematoxylin-eosin ; in growing eggs sometimes red, sometimes 

 blue or purple, even in eggs of the same size and of apparently 

 similar age. Its composition is thus somewhat uncertain and its 

 changes do not take place at any fixed or definite phase of the nu- 

 clear cycle. One or more small vacuoles are often present and 

 each of these usually contains a small spot or granule which 

 always stains red, regardless of the reaction of the rest of the 

 nucleolus. 



Near the end of the growth period the nucleolus becomes nearly 

 transparent, but usually shows a deeply staining cap upon 

 one side (fig. 27) which stains sometimes with acid sometimes 

 with basic dyes. It appears as if substances were leaving the 

 nucleolus during this period. Figure 27 suggests a connection 

 between the nucleolar cap and the chromosomes as though 

 nucleolar matter was passing into the chromosomes. This is not 

 necessarily true, for the masses of chromatin are often present only 

 in that side of the nucleus opposite the nucleolus and apparently 

 with no connection between, though the reticulum undoubtedly 

 furnishes an indirect pathway along which an interchange of 

 material might take place. 



A description of the cytoplasm at different stages will indicate 

 what changes occur. In the young oocj^te (fig. 25) the cytoplasm 



