DESCRIPTIVE PART. 



I. THE UNFERTILIZED EGG. MATURATION. 



Plate I. Phototype i. 

 The Ovarian Egg, before Maturation. 



The unripe ^g^, contained in the ovary, is characterized by the enormous size of the nucleus (called in this case the 

 '' germinal vesicle") and of the nucleolus (or '' germinal spot'') within it (cf. Text-fig. I. A). The protoplasm or cytoplasm 

 consists of a delicate network or reticulum (much better shown in some of the later figures) along the threads of 

 which are scattered minute granules, staining deep blue in hematoxylin, and generally known as microsomes. The 

 nucleus or germinal vesicle lies always in a somewhat excentric position. It is surrounded by a very distinct mem- 

 brane (which appears somewhat wrinkled in the photograph), and its interior is traversed by an irregular and 

 discontinuous network of chromatin, in which is suspended the muleolus or germinal spot (shown as a round black 

 spot in the phototype), stained, like the chromatin, deep blue by the haematoxylin. 



Close examination of the chromatic network shows that its threads are composed of minute separate granules 

 suspended in a clear achromatic substance, known as linin. The clear substance occupying the interspaces of the 

 network is probably a liquid, and is generally designated as the nuclear sap (Kernsaft). The substance of the 

 nucleolus differs widely in its chemical reactions from that of the chromatic network. 



The precise relation between the nucleus and the cytoplasm is still a matter of doubt. Most of the recent 

 works on the subject point to the conclusion that the linin network is of the same chemical nature as the cyto- 

 reticulum and is morphologically continuous with it (cf. p. 5). The linin network is, in other words, merely a 

 localized portion of the general cyto-reticulum enclosed within the nuclear membrane. The chromatin-granules 

 (forming the chromatic network) are embedded in the linin and surrounded by it. 



Plate I. Phototype 2. 



The Ovarian Egg before Maturatioii. 



An ovarian egg that has lain some time in water after extrusion from the ovary. This has caused the germinal 

 vesicle to swell considerably so that its size is somewhat exaggerated, and its excentricity is scarcely apparent. The 

 structure of the ovarian egg appears, however, with diagrammatic clearness. 



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