On the ffenerâtive Organs and Products of Tomopteris oniscifomiis E. 439 



gation of cells connected together, and not simply one large cell with 

 a large number of nuclei, as mi;^'ht be imagined (Fig. 17) when the 

 cell walls are not brought into relief by staining. The youngest free 

 masses are indistinguishaljle from the lobulated masses in tlie ovary, 

 and both take up a uniform stain when treated with borax carmine. 

 As ripening progresses the free masses of cells do not stain homo- 

 geneously throughout, for a number of deutoplasmic spherules are 

 now seen, especially in the largest cell of the group, Fig. 19, 21 deut. 

 The large cell seems to be increased at tiie expense of the smaller 

 cells till ultimately it forms a small ovum. I was able to trace in 

 many instances a gradual transition from a mass like that of Fig. 21 

 to the rii)e ovum represented in Fig. 25, which is an accurate drawing 

 to scale of an average sized large ovum. It is 0,248 mm in diameter. 

 The smallest of the ova is about half that size, and there is little 

 difference between the smallest ova and the largest cell of the most 

 advanced mass of cells. 



The ovum, when it is about ripe , after being treated with a 

 carmine stain has a slight yellowish tinge in colour, due to the pre- 

 sence of a large number of deutoplasmic spherules throughout its 

 mass. Fig. 24 deut. Small vacuoles are also seen in sections, Fig 24 vac. 

 The ripe egg (Fig. 25) at the time of fertilisation shows certain 

 nuclear changes, and for sometime afterward circulates in the coelomic 

 fluid like the unripe masses of cells. The nucleus exhibits a vacuol- 

 ation , Fig. 26 vac, which is soon followed by its division into two, 

 Fig. 27 n. The ovum at this time is generally slightly oval, but the 

 change in shape may be the result of the pressure already noticed, 

 rather than due to any difference in its behaviour brought about by 

 fecundation. The divided nucleus is composed of about equal portions, 

 but I was unable at this stage to observe any polar body expelled. 

 When, however, segmentation had taken place into a large macro-and 

 a small micromere I found the characteristic polar body. Fig. 28 p. h. 

 The deutoplasmic granules, deut, were almost uniformly distributed 

 throughout the mass of the macromere, mac, but the nucleated micro- 

 mere, mic, was composed almost exclusively of protoplasm. Segment- 

 ation took place regularly into two, four, eight, sixteen and thirty-two 

 micromeres. Figs. 29 — 32 mic. Amongst all the specimens which 1 

 examined containing oosphères, I never found any more advanced in 

 development than Fig. 32, and I must conclude that the oosphère 

 leaves the body of the mother about this time. The macromere is 

 seen to 1)€ surrounded with a very thin pellicle which , in the most 



