EARLY STAGES OF DEVELOPMENT OP THE RABBIT. 125 



Nor is there any regularity, as far as I have observed, as to 

 the location of the large and small spheres. Figs. 12, 15, and 

 17 show this very well. 



Fig. 12 was drawn with camera while the specimen was still 

 fresh in a drop of aqueous humour of the rabbit. 



After the drawing had been made the specimen was placed 

 in Perenyi's fluid and subsequently freed from the zona pellu- 

 cida with fine needles. The segments were then separated one 

 from another. In all there were seventeen segments, and of 

 very different sizes. 



Fig. 13 shows three of the segments thus separated. Except 

 in size I could detect no difference. 



Another specimen from the same Fallopian tube was placed 

 in I per cent, solution of silver nitrate for two minutes, and 

 after having been washed in water and exposed to the sun for 

 a few hours was embedded in paraffin and cut. 



Fig. 20 is from a section through about the centre of this 

 specimen. The nuclei of the individual segments are not at 

 all distinct, excepting where they have been cut almost through 

 their centres, as no other stain except silver nitrate has been 

 used. 



(Of all methods of fixing the early segmenting stages, I 

 believe none answer so well, as far as concerns the preservation 

 of the correct shape of the spheres, as a weak solution of silver 

 nitrate allowed to act for not more than two minutes. Next 

 to silver nitrate I believe osmic acid, 2 per cent., is best.) 



Fig. 15, which is a specimen from a rabbit killed sixty-six 

 hours and a half after coition, exhibits in a very remarkable 

 way the great diflference in size which may sometimes occur 

 between the several segments. 



From the forty-fifth to the seventieth hour the segmentation 

 proceeds slowly, and, I am inclined to think, sometimes very 

 irregularly, as shown by the last-mentioned specimen (fig. 15). 



In sections of these stages I do not notice anything particu- 

 larly remarkable, except that I have completely failed to find 

 any constant character Avhereby the inner cells can be distin- 

 guished from the outer. Fig. 21 is of a section through the 



