OBSERVATIONS ON THE MATURATION PROCESSES. 25 



VII. OBSERVATIONS ON THE MATURATION PROCESSES. 



In considering the various topics of maturation the processes are 

 dealt with by stages, the chief characteristics of which have been briefly 

 suggested in table 2 (p. 14). It seems desirable, however, to give a more 

 precise definition of these stages before proceeding to a detailed account 

 of maturation. 



It should be borne in mind that these stages, though fairly distinct, 

 are, nevertheless, only periods in a continuous process of development 

 and therefore connected with each other by intermediate conditions. 



A. OOCYTE I. 

 l. GENERAL DESCRIPTION OF STAGES. 



STAGE I. GERMINATIVE VESICLE. 



The germinative vesicle, nearly up to the time when it is trans- 

 formed into the first maturation spindle, presents the following condi- 

 tions (compare plate i, fig. i): 



It is somewhat eccentric in position, nearly spherical, and from 19 

 to 26 (on the average 23) micra in diameter. It has a uniformly thin, 

 lightly staining, smooth membrane, and is filled with a clear, homo- 

 geneous substance, the karyoplasm. At one side lies the vesicular 

 nucleolus, usually in contact with the nuclear membrane. Immediately 

 inside the membrane, and particularly around the nucleolus (plasmo- 

 some), are masses of chromatic substance attached to these structures 

 by achromatic material of irregular, though often threadlike, form. 

 There are a few strands, remnants of the linin network of an earlier 

 stage, running through the karyoplasm. Figure i, plate i, illustrates 

 these conditions, except for the condition of the nuclear membrane. 



The spheroidal, or sometimes lenticular, nucleolus is about 8.5 micra 

 in its longest diameter, and has a fairly thick, deeply staining wall of uni- 

 form thickness. It contains only a clear, homogeneous substance, never 

 any chromatic bodies such as are attached to its outer surface, either as 

 distinct bodies or as apparent thickenings of its membrane (fig. i). 



The chromatic masses of the nucleus are usually globular, though 

 sometimes of an irregular form, and have no correspondence with chro- 

 mosomes of later stages either in number or in shape. In phospho- 

 tungstic-acid haematoxylin some of them are stained deep blue, like 

 chromatin; a few pink, like cytoplasm. There are in addition deeply 

 stained granules scattered through the nucleus. These are usually 

 associated with the achromatic substance. 



Preparatory to the advent of the first spindle, the germinative 

 vesicle moves a little nearer the surface of the egg, but the depth at 

 which it comes to lie is not the same in all cases. It then decreases in 

 size, and its membrane becomes a little fainter and presents a very 

 irregular, wrinkled appearance (fig. i). 



