230 DEVELOPMENT OF ELASMOBRANCH FISHES. 



All these bodies occupy the place of an ordinary nucleus, 

 they stain like an ordinary nucleus and are as sharply denned 

 as an ordinary nucleus. 



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 1 , 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 

 stage 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 = -j^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 frequently 

 irregular in shape and often provided with knob-like processes. 

 The gradations are so complete between typical nuclei and 

 bodies like that shewn (PI. 6, 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. 7). 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 difficulty 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 re- 

 markable since in the early stages of segmentation, when very 

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

 uncommon ; 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. 



1 Loc. cit. 



