166 p. KIDD. 



of the " couche intermediare " closely resembles that of the 

 germ ; it is nucleated and finely granular like the germ, 

 but as a rule the granules are rather coarser here than 

 in the germ. The nuclei resemble those of the germ. 

 He does not regard the nuclei of the '^ couche inter- 

 mediare " as derived from the nucleus which appears in the 

 germ on fertilisation, i.e. after disappearance of the germinal 

 vesicle, but distinguishes them from the nuclei of the germ 

 cells proper. 



Klein, in the April number of this Journal, 1876, has 

 described the changes occurring in the subgerminal layer, 

 or " Parablast," as he calls it, in the early development 

 of the ova of Trout. He describes the '' parablast " 

 (which he distinguishes from the " archiblast " or blas- 

 toderma) as existing in the earlier stages in the form of 

 a peripheral wedge-shaped mass like van Bambeke's 

 "bourrelet," and provided with a large number of nuclei of 

 a rather peculiar character. The nuclei resembled those of 

 the germ in being vesicular and pale, and in many cases 

 were deeply notched or divided into lobes ; round nuclei 

 were not often seen. Klein draws a sharp distinction between 

 the " parablast " or subgerminal layer, and the white yolk, 

 and gives several reasons for not regarding the former as 

 white yolk. He describes the large formative cells as 

 arising from the parablast, and gives several drawings repre- 

 senting large nucleated masses arising from the finely gra- 

 nular nucleated " parablast." 



Balfour ( ' Journ. Anat. Phys.,' April, 1876) in one part of 

 his communication on the development of Elasmobranch 

 Fishes, describes nuclei in the upper part of the yolk beneath 

 the segmentation cavity, and found that the nucleated yolk 

 undergoes cleavage. Balfour regards the " couche inter- 

 mediaire," '*' parablast," or subgerminal layer as yolk, and 

 speaks^f the " nuclei of the yolk." 



We shall now describe more particularly the appearances 

 in our ovvn cases. In all the seven blastoderms which we 

 have previously referred to, the blastoderm rested on a finely 

 granular bed, the subgerminal layer or ''parablast " (Klein). 

 The extent of this layer varied in different specimens. The 

 characters of this layer were very definite. Under low 

 powers it had an extremely finely granular appearance, and 

 looked as if it had been dusted over lightly with a fine 

 powder. It resembled the blastoderm in appearance very 

 closely ; but, as was noticed by van Bambeke in Teleostean 

 Fishes, the granules of the subgerminal layer were slightly 

 coarser than those of the germ. Where the sections were 



