OF THE VERTEBRATE OVARY. 565 



definitely surrounded by granular protoplasm than the other 

 nuclei of the nests, and accordingly have their outlines more 

 sharply defined. Between nuclei of this kind, and others as 

 large as those of the permanent ova, there are numerous transi- 

 tional forms. The larger ones frequently lie in a mass of 

 granular protoplasm projecting from the nest, and only united 

 with it by a neck (PI. 24, figs. 14 and 16). For prominences of 

 this kind to become independent ova, it is only necessary for 

 the neck to become broken through. Nests in which such 

 changes are taking place present various characters. In some 

 cases several nuclei belonging to a nest appear to be undergoing 

 conversion into permanent ova at the same time. Such a case 

 is figured on PL 25, figs. 17 and 18. In these cases the amount, 

 of granular protoplasm in the nest and around each freshly 

 formed ovum is small. In the more usual cases only one or 

 two permanent ova at the utmost are formed at the same time, 

 and in these instances a considerable amount of granular proto- 

 plasm is present around the nucleus of the developing perma- 

 nent ovum. In such instances it frequently happens several of 

 the nuclei not undergoing conversion appear to be in the process 

 of absorption, and give to the part of the nest in which they are 

 contained a very hazy and indistinct aspect (PI. 24, fig. 15). 

 Their appearance leads me to adopt the view that while some 

 of the nuclei of each nest are converted into the nuclei of the 

 permanent ova, others break down and are iised as the pabu- 

 lum, at the expense of which the protoplasm of the young ovum 

 grows. 



It should, however, be stated, that after the outlines of the 

 permanent ova have become definitely established, I have only 

 observed in a single instance the inclusion of a nucleus within 

 an ovum (PI. 25, fig. 24). In many instances normal nuclei of 

 the germinal epithelium may be so observed within the ovum. 



The nuclei which are becoming converted into the nuclei of 

 permanent ova gradually increase in size. The following table 

 gives the diameter of four such nuclei : 



o'O22 mm. 

 ox>22 mm. 

 0x124 mm. 

 0x132 mm. 



