208 



RICHARD ASSHETON. 



obtained from them forty specimens. Of these thirty-one 

 were perfect embryos, and nine were apparently unfertilised 

 ova. 



From fourteen of these sheep I obtained two specimens in each 

 case, from twelve only one apiece. In the remaining fourteen 

 I was unable to find any embryo, although I think the 

 majority probably were pregnant. The approximate ages of 

 these were as follows : 



Segmentation of the Ovum. 



In one respect I have been very unlucky. I tried with six 

 sheep to obtain the earliest stages of segmentation. I 

 have, however, not succeeded in getting any stage between the 

 fertilised but unsegmented ovum, and a stage with six segments. 

 The earliest specimens I have are two taken from the oviducts 

 of sheep killed during the second day. Each ovary showed a 

 small bright red corpus luteum. In each side an ovum was 

 found about halfway down its oviduct. In each case the ovum 

 was slightly retracted from the zona radiata, leaving a space at 

 one side. The ovum of the sheep is large, measuring as much 

 as '15 mm. in diameter, or including the zona radiata "18 mm. 

 while fresh. 



These specimens were preserved in '5 per cent, chromic 



