OVARY AND INTKA-OVARIAN EGG IN TELEOSTEANS. 309 



unripe condition it is so ; but as development of the ova proceeds, 

 the lumen becomes more and more closed by the extension of the 

 lamellae towards the centre of the organ. 



At the time when a section shows an appearance similar to that 

 shown in fig. 2 the lumen disappears, and the lamellge become 

 indistinguishable on account of their closely packed and fused con- 

 dition. Ultimately, by the thinning out and rupture of the epithelium, 

 the almost ripe ova lie free in the organ, ready for extrusion. 



The outer wall consists of fibrous tissue, which assumes different 

 appearances according to the sexual condition of the ova. The 

 fibres run, for the most part, in a longitudinal direction, and 

 are therefore seen best in longitudinal sections. The outer 

 fasciuli, however, frequently bend until they lie transversely. 

 From the main membrane, offshoots spring towards the interior of 

 the organ. These pass off in a curved manner, similar to the spokes 

 of an iris diaphragm, although by no means so regularly. 



The offshoots form the leading divisions of the internal arrange- 

 ment, and on their branching afford support to the lamellae in much 

 the same way as veins do in the leaves of plants. 



In what we may describe as the resting stage in the common 

 dab — for I certainly believe that a condition of this sort obtains 

 — when after spawning the ovary has been made up with quite unripe 

 eggs, the outer wall has a thickness of about '9 mm. 



In following the various conditions of the ovary we find that the 

 condition of its outer wall fluctuates in a rather singular manner, 

 that in the cycle from one resting stage to another it thickens 

 twice, and thins again twice. From the "9 mm. thickness it 

 gradually grows until, when the ova are what has been described 

 as half ripe (fig. 2), (when the lumen of the ovary disappears) it 

 reaches the thickness of from "19 to "20 mm. This is its maximum 

 thickness in the purely laminated fibrous condition. The organ now 

 increases rapidly in size, and as it does so the outer wall decreases 

 in thickness, the fibrous composition being less and less evident as 

 this goes on. When the ova are ripe the thickness is only from "2 

 to '3 mm. in the common dab. 



Whenever the process of spawning releases the pressure, the wall 

 rapidly thickens again, and when spawning is completed and the 

 organ is in its flaccid condition, a distinct division into an outer and 

 an inner layer is noticeable. The outer is still the normal fibrous 

 envelope, but the inner coat becomes highly modified. Numerous 

 nuclei make their appearance (fig. 11), and increasing by a process 

 of division, first of all form thickened masses, and then by the 

 bursting of the inner membrane are poured out, and form irregular 

 masses amongst the vacuoled eggs at the periphery of the ovary. 



