148 J. T. OUNNINaHAM. 



in ova smaller than that figured, and are visible as separate 

 elements in the larger up to those of a diameter of '43 mm. 



The sections from which fig. 8 is taken were prepared 

 from material fixed immediately after the death of the 

 fish in a mixture of picro-sulphuric acid and spirit. The 

 feathery fibrils in these can only be faintly traced with diffi- 

 culty, as they are scarcely stained at all. They are more distinct 

 in the younger eggs. Fig. 30, PI. 4, represents the vesicle of 

 the most advanced egg in these sections. Although there are 

 empty follicles showing that ripe eggs have escaped, there are 

 no stages more advanced than that figured. Fig. 9 shows the 

 structure of the most advanced egg in sections from part of 

 the ovary of a gurnard fixed with chromic acid i per cent. 

 In the younger eggs the feathery fibrils can be seen, but in 

 this stage in these sections they cannot be distinguished. 

 The nuclear substance appears pale and granular. The ovum 

 represented is "53 mm. in diameter. 



The history of the nucleoli in the ova of other animals has 

 been much debated, and although the transformations of the 

 germinal vesicle have been recently traced completely and in 

 detail in certain cases, there is still room for doubt concerning 

 the significance of the changes which are observed. In 1887 

 O. Schultze stated that in the nearly ripe egg ofEana fusca 

 there was no chromatin network ; that the nucleoli formed a 

 rounded group in the germinal vesicle, in the centre of which 

 were very minute corpuscles. He believed that these corpuscles 

 were derived from the disintegration of nucleoli, and that they 

 united together to form the chromosomes, which afterwards 

 united into a convolution. He also saw some nucleoli dissolve 

 into liquid. 



Professor G. Born, in 1892, made an exact investigation of 

 the development of the first directive spindle in the ovum of 

 another Amphibian, Triton tseuiatus. He found that the 

 chromatic convolution was not derived from the nucleoli, but 

 as Riickert described in Selachians, from chromatic fibrils 

 previously present. These fibrils are very imperfectly seen 

 after staining in mass with borax carmine, but are to be 



