For a slightly older stage than Q, the two annexed tables also shew the comparative size of the modified and unmodified nuclei:
Unmodified nuclei of normal primitive ova—
0.014 mm.
0.016 mm.
0.014 mm.
0.016 mm.
0.016 mm.
Nuclei of primitive ova with modified nuclei—
| Nuclei. | Granular Bodies in nuclei. |
|---|---|
| 0.018 mm. | 0.008 mm. |
| 0.016 mm. | 0.008 mm. |
| 0.016 mm. | 0.010 mm. |
| 0.016 mm. | |
| 0.018 mm. |
These figures bring out with clearness the following points: (1) that the modified nuclei are slightly but decidedly larger on the average than the unmodified nuclei; (2) that the contained granular bodies are very considerably smaller than ordinary nuclei.
Soon after the appearance of the modified nuclei, remarkable changes take place in the cells containing them. Up to the time such nuclei first make their appearance the outlines of the individual ova are very clearly defined, but subsequently, although numerous ova with but slightly modified nuclei are still to be seen, yet on the whole the outlines of all the primitive ova are much less distinct than before; and this is especially the case with the primitive ova containing modified nuclei.
From cases in which three or four ova are found in a mass with modified nuclei, but in which the outline of each ovum is fairly distinct, it is possible to pass by insensible gradations to other cases in which two or three or more modified nuclei are found embedded in a mass of protoplasm in which no division into separate cells can be made out (fig. 14). For these masses I propose to employ the term nests. They correspond in part with the Ureiernester of Professor Semper.
Frequently they are found in hardened specimens to be enclosed in a membrane-like tunic which appears to be of the nature of coagulated fluid. These membranes closely resemble and sometimes are even continuous with trabeculæ which traverse the germinal epithelium. Ovaries differ considerably as to the time and completeness of the disappearance of the outlines marking the separate cells, and although, so far as can be gathered from my specimens, the rule is that the outlines of the primitive ova with modified nuclei soon become indistinct, yet in one of my best preserved ovaries very large nests with modified nuclei are present in which the outline of each ovum is as distinct as during the period before the nuclei undergo these peculiar changes (Pl. 24, fig. 12). In the same ovary other nests are present in which the outlines of the individual ova are no longer visible. The section represented on Pl. 24, fig. 2, is fairly average as to the disappearance of the outlines of the individual ova.
It is clear from the above statements, that in the first instance the nests are produced by the coalescence of several primitive ova into a single mass or syncytium; though of course, the several separate ova of a nest may originally, as Semper believes, have arisen from the division of a single ovum. In any case there can be no doubt that the nests of separate ova increase in size as development proceeds; a phenomenon which is more reasonably explained on the view that the ova divide, than on the view that they continue to be freshly formed. The same holds true for the nests of nuclei and this, as well as other facts, appears to me to render it probable that the nests grow by division of the nuclei without corresponding division of the protoplasmic matrix. I cannot, however, definitely prove this point owing to my having found nests, with distinct outlines to the ova, as large as any without such outlines.