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Part III. — Sixteenth Annual Report 



neighbourhood will be observed a number of minute stained granules, 

 similar to those within the other nucleoli, and which have doubtless 

 escaped from it. In the central area enclosed by the circle of nucleoli, 

 and which is more translucent than the rest of the germinal vesicle, 

 another appearance is visible. The delicate moniliform linin network 

 will be observed as the morphological basis, and here and there are chains 

 of minute stained granules, arranged in curves which represent the 

 chromatin threads usually described, or chromosomes. 



The central area, as has been said, is much more translucent than 

 the rest of the germinal vesicle, the linin network is more loose and open, 

 and the contents no doubt more fluid, and probably the seat of more 

 active chemical changes. The proximity of the ring of disintegrating 

 nucleoli, which move into this position where the chromatic chains are 

 distinct, must be noted ; and one is tempted to suggest that the 

 escaped nucleolar granules undergo further metamorphosis to form the 

 chromatic chains. It will be observed in the figure that some of the 

 minute isolated spherules or granules (6) are of a different character 

 from the rest, as if they were undergoing granular disintegration ; 

 there are also a number of highly-stained granules scattered through 

 the karyoplasm. This explanation agrees with that put forward 

 by Cunningham to account for the absence of nucleoli and the presence 

 of irregular chromatic rod-like bodies, obviously derived from the 

 nucleoli, in the nearly mature ova of the turbot.* But if this view of 

 the fate of the nucleolar contents is correct it will not, I think, apply to 

 all of them, because in the germinal vesicle of the egg of the angler 

 undergoing the hydrolytic change at maturation numerous granules, 

 similar to those described, are to be seen scattered in the substance of 

 the germinal vesicle. Many of these are extremely faint in outline, and 

 appear to be fading or dissolving away (Fig. 4, PI. III.). 



I may here say that my observations on the characters of the germinal 

 vesicle support the opinion of Cunningham — " that the multiplication of 

 *' nucleoli in the teleostean ovum, and their disappearance at a later stage, 

 *' are effected by the streaming of chromatin along threads of linin." As 

 previously stated, in the germinal vesicle of the minute eggs examined 

 a somewhat coarse, irregular network is readily perceived, with a 

 number of small nucleoli scattered throughout it. These are obviously 

 at this stage karyosomes, and they appear to be due to the collection at 

 the nodes of the network of semi-fluid chromatic substance, in very 

 different amounts, so that the droplets are of various sizes. As they 

 increase in dimensions they either separate from the node or dwarf it. 

 At all events in sections they appear as isolated bodies, and they flow to 

 the periphery at an early stage, and become disposed in apposition to 

 the membrane at fairly regular intervals prior to the formation of yolk 

 or diff'erentiated cytoplasm, a site which they continue to occupy to 

 nearly the close of ovarian growth. At the same time the rest of the 

 germinal vesicle becomes more and more achromatic. The view which 

 has been put forward that the nucleoli are of little importance in the 

 ovum, and may be even regarded as by-products or efi'ete matter result- 

 ing from nuclear activity, is, I am sure, inapplicable to the teleosteau 

 egg. On the contrary, their number, size, position, and history show 

 that they perform an important role in the metabolism of growth, the 

 formation of the cytoplasm, and probably of the yolk. On the 

 hypothesis that the secretion of the follicular cells during the 

 whole period of the growth of the ovum has the same composition as the 

 free ovarian fluid, it is obvious that it must undergo very considerable 



* Op. cit., pp. 146, 147, 159. 



