13 SEGMENTATION. 



There is present around some of these, especially those 

 situated in the yolk, the network of lines of the yolk de- 

 scribed by me in a preliminary paper ^ and I feel satisfied that 

 there is in some cases an actual connection between the net- 

 work and the nuclei. This network I shall describe more fully 

 hereafter. 



Further points about these figures and the nuclei of this 

 stasre I should like to have been able to observe more com- 

 pletely than I have done, but they are so small that with the 

 highest powers I possess (Zeiss, Immersion No. 2 = -f-^ in.) their 

 complete and satisfactory investigation is not possible. 



Most of the true nuclei of the cells of the germinal disc 

 are regularly rounded ; those however of the yolk are fre- 

 quently irregular in shape and often provided with knob-like 

 processes. The gradations are so complete between typical 

 nuclei and bodies like that shewn (PL ii. fig. 8 c) that it 

 is impossible to refuse the name of nucleus to the latter. 



In many cases two nuclei are present in one cell. 



In later stages knob-like nuclei of various sizes are scattered 

 in very great numbers in the yolk around the blastoderm (vide 

 PI. III. IV. v.). In some cases it appears to me that several of 

 these are in close juxta-position, as if they had been produced by 

 the division of one primitive nucleus. I do not feel absolutely 

 confident that this is the case, owing to the fact that in the 

 investigation of a knobbed body there is great difiiculty in 

 ascertaining that the knobs, which appear separate in one plane, 

 are not in reality united in another. 



I have, in spite of careful search, hitherto failed to find 

 amongst these later nuclei cone-like figures, similar to those I 

 found in the yolk during segmentation. This is the more remark- 

 able since in the early stages of segmentation, when very few 

 nuclei are present in the yolk, the cone-like figures are not un- 

 common ; whereas, in the latter stages of development when 

 the nuclei of the yolk are very common and obviously increas- 

 ing rapidly, such figures are not to be met with. 



In no case have I been able to see a distinct membrane 

 round any of the nuclei. 



I have hitherto attempted to describe the appearances 



^ Loc. cit. 



