THE OVUM OF THE NINE-BANDED ARMADILLO. llj 



VII. NUCLEAR CHANGES DURING THE GROWTH PERIOD OF THE 



OVOCYTES. 



The nuclear changes from the time when the ovocyte is in the 

 primordial follicle stage till the establishment of the first cleavage 

 spindle constitute the prophases of maturation. The earlier as 

 well as the later changes should receive attention. Students of 

 mammalian ovogenesis, however, have as a rule restricted their 

 observations to the changes immediately connected with matura- 

 tion divisions, ignoring the long period of nuclear and cell 

 differentiation that leads up to and doubtless conditions these 

 divisions. The following account makes no claim of compre- 

 hensiveness but will serve to suggest some of the more significant 

 phases of nuclear behavior that are characteristic of this period. 



The nucleus of the ovocyte in the primordial follicle (Fig. 19) 

 shows the chromatin in the form of long, more or less coiled 

 threads, which are sometimes so tangled as to form a pseudo- 

 reticulum. In neutral stains such as iron haematoxylin and 

 copper chrome hsematoxylin the chromatin threads and the 

 plasmosome take the same stain, but when double staining 

 methods are employed the difference between the two materials 

 is clearly brought out. When neutral safranin and acid violet 

 are used the chromatin takes the violet color from the acid 

 reagent and the plasmosome takes only the neutral color, appear- 

 ing bright red. With toluidin blue and acid fuchsin the chro- 

 matin takes a red color from the acid dye and the plasmosome is 

 stained bluish with the basic stain. With thionin and erythrosin 

 the chromatin takes a red color from the acid erythrosin and 

 the plasmosome is stained purple from the thyonin. Evidently 

 then at this period the chromatin is basic and the plasmosome 

 acid in character. The plasmosome is also shown to be a 

 vesicular structure containing some vacuoles or granules. It is 

 practically certain also that the chromatin threads, each of which 

 must be identified as an elongated chromosome, are diploid in 

 character, since synapsis has occurred during the organogenesis 

 of the ovary. It is only in later stages that the diploid composi- 

 tion of these bodies manifests itself. 



In the early simple epithelial stage of the follicle no marked 



