THE SEI WHALE 



245 



The mean diameter of the largest corpus luteum b co-existing in the ovaries with a 

 corpus luteum a is 3-22 cm., with a maximum of 4-1 cm. and a minimum of 2-1 cm. 

 The only recorded corpus luteum of lactation is 3-0 cm. in mean diameter, so that it 

 has almost completely degenerated into a true corpus luteum b. 



Data of the ovar}' weights are few for this species, but the figures available are plotted 

 in Fig. 70 against total body length, immature, mature, resting, lactating, ovulating 

 and pregnant whales being separated. It will be seen that until maturity is reached, at 

 about 14-5 m. total length, the weight of the ovaries increases slowly with body length, 

 but that after maturity is reached the relation between ovary weight and total length 



5- 



c 



a. 



•c 3- 



o 



% 



■^ Z 



-op 



i 



• Resting 



• Inn mature 

 ® Lactdting 

 O Ovulating 

 @ Pregnant 



® 



® 



® 



o 



... » 



12 



13 



—I — 

 14 



— r- 

 15 



16 



17 



Total Length in nnetres 



Fig. 70. Sei whale. Females. Ovary weights. 



is not preserved so closely and wide variations occur. A decline in weight in the largest 

 whales is indicated, similar to that which probably occurs in the other species of 

 balaenopterid whale. The presence of large corpora lutea makes the weight in pregnant 

 whales average over twice that in resting whales. The weight of the ovaries in this 

 species is very much less than in the Fin and Blue whales, the heaviest non-pregnant 

 ovaries weighing little over 2 lb., whereas non-pregnant ovaries of over 9 and 14 lb. 

 have been recorded for the other two species respectively. 



Fig. 71 shows the number of corpora lutea in the ovaries plotted against the total 

 length of whale. Though the ovaries of the smallest whales contain only a small number 



