of the Fishery Board for Scotland. 



129 



The smallest of these ova differ only in appearance from the few 

 spherical epithelial cells above referred to in the layer at the base of 

 the pouch in bein^? larger and in having the scanty reticulum some- 

 what better dehned. One measured 0-0056mm., and the highly- 

 stained granule, or nucleolus, in the interior was not above J^^th 

 of the diameter ; the diameter of one of the round epithelial cells 

 outside the pouch was about 0 0035mm. In those a little larger, mea- 

 suring about O'OOSmm. in diameter, no single prominent stained granule 

 or nucleolus can be seen, but the network is now very obvious, though 

 somewhat scanty, the meshes being larger and the threads very finely 

 granular, and there are a number of minute net-knots brightly stained. 

 In the germinal vesicle, as it may now be called, 0*011 mm. in diameter, 

 the network has obviously increased and become closer, the meshes being 

 smaller and the karyosomes more numerous, but still minute. The general 

 appearance of all these stages is a clear transparent vesicle with a slender 

 network that seems in the smaller ones to be chiefly arranged against the 

 inner surface. In some of the size stated (0*01 1mm.) a faint crescent may 

 be detected, at one side in which are a number of stained granules looking 

 like nucleoli. In eggs somewhat larger the cytoplasm consists very fre- 

 quently of a crescentic cap placed at one end of the usually ovate germinal 

 vesicle, or when the germinal vesicle is spherical it is arranged around it 

 more regularly. For example, an egg with a germinal vesicle, 0*0 16 8mm. 

 by 0 •028mm., was destitute of cytoplasm except at one end, where it 

 extended 0*01 1mm. in a rapidly tapering cap. The wall of the germinal 

 vesicle was very delicate and everywhere highly stained, and it con- 

 tained a very dense achromatic network, towards the centre of which 

 what seemed to be minute granules could be indistinctively perceived. 

 The most striking difference in the germinal vesicle, as compared with 

 the previous stage, is the presence of a few minute brightly-stained 

 nucleoli at the periphery, the comparative absence of karyosomes, 

 and the dense network. The cytoplasm, as in all small teleostean 

 eggs, is very highly stained, and in these preparations it contains a 

 large number of highly-stained particles as large as the nucleoli, 

 the matrix, which is finely granular, being also highly stained. In 

 eggs a little larger these stained bodies are also conspicuous ; some of 

 the larger are surrounded by a narrow clear zone, like yolk-nucleoli, and 

 in some cases they are disposed in ball-like clusters. I have been 

 able to trace them into the conspicuous yolk-nucleus present in eggs 

 a little more developed. The appearance of the cytoplasm in eggs 

 measuring about 0-12mm. shows a coarsely granular appearance, but 

 not the presence of the definite particles described, and it is less 

 deeply stained. The appearances in the ova above described are 

 consistent with the growth in the germinal vesicle of the minute 

 eggs of a dense network, the formation of karyosomic nucleoli in this 

 network, the growth and transference of these to the periphery of 

 the vesicle as the characteristic nucleoli, with marked achromatic 

 appearance of the network, and their transference to the cytoplasm 

 around. In these pouches of the angler the gradation of the depth 

 of staining of the cytoplasm in eggs of different sizes is very well 

 shown, the small ones at the bottom of the pouch being most intensely 

 coloured, the depth of tint diminishing as the size increases. In the 

 larger eggs in these sections, measuring about 0 08mm., a yolk-nucleus is 

 distinct. With a low power it appears as a round body, more deeply 

 stained than the cytoplasm, and surrounded by a pale zone; sometimes 

 it is flattened out and ovate at the extreme periphery, sometimes close to 

 the wall of the germinal vesicle ; in one case it lay over the germinal 



