OVARY AND INTEA-OVARIAN EGG IN TELEOSTEANS. 301 



circumference, owing to the extension of the light protoplasm alone, 

 while the dark protoplasm and nucleus remain as before. A condi- 

 tion is presently reached where this extension causes the light to 

 separate from the dark, so that a cavity is formed around the dark 

 centre with its contained nucleus, i. e. around what must now be 

 considered as a complete ovum in itself. The light protoplasm 

 then appears to diminish in extent until only a margin is left inside of 

 what was the old investing membrane. 



The cast-off membranes of neighbouring eggs coming in contact 

 with each other, and the light protoplasm being almost completely 

 absorbed, the appearance becomes that of trabeculge. The contained 

 spaces are occupied by the ova, and the interstices become filled up 

 by fresh ova of a small size, formed from epithelial cells in a manner 

 to be described at a later stage. 



I. The Great Ova, or those which are to he extruded at the first 



spawning period. 



In the ovary of a common dab which is approaching ripeness 

 (fig. 2) the large ova are well marked. The zona radiata has thick- 

 ened, and the protoplasm of the egg shows a distinctly reticulated 

 structure. The nuclear membrane has disappeared, the nucleus 

 now appearing as a clear area, either surrounded by or scattered 

 over with the numerous nucleoli, occupying an eccentric position in 

 the ovum. 



The nucleoli are much more circular in shape than is the case in 

 eggs of an earlier stage, and when they are arranged round the 

 periphery of the clear area there are numerous very minute bodies 

 of exactly the same appearance to be found in the area itself. 

 These minute bodies must also be considered as nucleoli, for from 

 an examination with a very high power I find that they are 

 budded oif from the large nucleoli at the margin of the clear area, 

 and then travel inwards towards the centre. Fig. 3 is drawn from 

 an ovum in the same section as is represented by fig. 2, and suffi- 

 ciently represents the appearance indicated. These small bodies, 

 by enlarging, form another condition of the nucleus seen at this 

 stage. The parent nucleoli seem to give oif many buds in this way, 

 until, having lost much of their old constitution, they stain feebly, 

 and are difficult to distinguish from the coarser granules of sur- 

 rounding protoplasm. 



There is, therefore, among Teleosteans a more or less distinct 

 congregation of nucleoli in the centre of the degenerating nucleus, 

 similar to that described by Iwakawa (5) in the egg of Triton at a 

 different stage. This author concludes that the nucleoli, or, as 



