PLATE XLI 



Fig. I. Ovaries of a lactating Fin whale, No. i68. The body on tlie side 

 of the right-hand ovary is the recent corpus luteum of pregnancy. 



Fig. 2. Ovaries of Blue whale, No. io6, with only four old corpora lutea 

 which have not undergone much retrogression. 



Fig. 3. Series of old corpora lutea from one pair of Fin whale ovaries, 

 seen in section. 



