34 Fisher 11 Board for Scotland. 



layers of eggs ; it prol)n,l)ly is the follicle of the ovum. In the centre 

 are the blood vessels {l>r.), and on either side are the ova. A loop (/>?'') 

 from the blood vessels is shown encircling each egg. 



There appear to be differences among the blood vessels. The main 

 blood vessels have walls composed of fibres, while the small blood 

 vessels in the ovarian tissue have a wall of two layers at least, a fibrous 

 layer and a cellular layer. The cellular wall consists of small round 

 nucleated cells. 



The skin that covers an unyolked egg (irmn.) is thin ; that which 

 covers a yolked egg is thick (yk, Fig. 102). In the follicle of the 

 latter there is between the outer skin and the zona of the egg a thick 

 layer of round cells (2^l., Fig. 104). This laj'-er extends into the stalk 

 of the egg. This placental laj^er is evidently attached to the vascular 

 laj'er (vas.), but is independent of the follicle (fl.). It apparently comes 

 away with the egg when the follicle is ruptured. The cells composing 

 the layer are similar to the round nucleated cells of the basement 

 layer. Such cells may be seen along the vessels and concentrated in 

 gland-like bodies. The follicle, although cellular, is more dotted and 

 not distinctly cellular on the stalk portion. 



The modus seems to be as follows. The egg which is about to 

 ripen has a layer of round cells developed round it. How they arise 

 is not clear. Whether they are developed hi, situ or transferred there 

 is an open question. This cellular laj^er, which is a sort of placenta, 

 apparently secretes the yolk which the egg absorbs. The j^olk con- 

 sists of small corpuscles. 



The egg-columns are thickly arranged over the surface of the ovary. 

 They are not all of the same height. The yolked eggs are often 

 terminal ; some, however, come ofi" the side, and even well down at the 

 base of the column. 



In Januaiy the ovaries in fishes 39 and 41 cm. long had not 

 developed far towards ripeness. A few white j^olked eggs measured 

 •27 mm. in diameter. The nucleus was visilale. The clear eggs 

 measuring •25 mm. in diameter had some white pigment round the 

 edge of the nucleus. 



In February fishes measuring 28"5 and 35 to 41 cm. in length 

 were examined. In the fish 28'5 cm. long a small (though long) 

 immature ovary was found. 



The ovaries in the others was very similar to those examined in 

 January. The naked-eye appearance of the ovar}^ was almost 

 colourless, with only a pale pink colouration. Most of the eggs were 

 clear. Some -were beginning to store up yolk. The yolked eggs 

 measured up to '27 mm. in diameter. Here and there in the ovarian 

 tissue there were patches of white granular matter (gr., Fig. 109). It 

 appears to be a coagulated albuminous matter. It was observed in 

 more than one ovarj', and in one case it was in greatest c[uantity in 

 the oviduct. In parts it had assumed a cellular form. 



In March a female 40 cm. long was obtained. The largest yolked 

 eggs were ^35 mm. in diameter. An enlarged portion of the ovary, 

 which had been cleared with a solution of sodium -hydrate, is shown 

 in Fig. 105. Some of the terminal eggs have long stalks. The 

 small eggs appear to be more numerous than in the ovaries examined 

 previously. 



Some of the ^\•hite granular matter was seen in the ovarj^ (ijr., Fig. 

 105). The general structure of the ovary in this fish would suggest 



