THE SEI WHALE 243 



was present in one out of seven immature whales (i4"3 per cent) and a tag representing 

 the remains of the band was present in three out of fifty-two adult whales examined 

 (5-45 per cent). These figures may be compared with those from the Fin whale in which 

 the band is present in 21-4 per cent of immature whales, and a tag in 6-8 per cent 

 of adults. 



The teats are place in the mammary grooves, situated one on each side of the vulva. 



In one female Sei whale a deep groove ran from the genital groove to the umbilicus. 

 It was pregnant (whale No. 1754) and a similar groove was present in the foetus, which 

 measured 3-68 m. in length. 



A number of observations were recorded on the state of the vulva and vagina in Sei 

 whales, but it is difficult to make definite correlations between the conditions found 

 and the stages of the oestrous cycle. The data are summarized in Table XIX from which 

 it will be seen that only broad conclusions can be drawn. The figures show the numbers 

 of whales examined in each group. Dealing first with the vulva, it is tightly closed, 

 though structurally patent, in all immature whales, but open in varying degrees in 

 resting, ovulating and lactating whales. In pregnant whales it is nearly twice as fre- 

 quently open as closed. It was noted as congested in some whales in all conditions 

 except lactation, most frequently in pregnant whales. 



The vagina was found to be congested more often than not in whales in all conditions, 

 most frequently in resting whales. In many immature and pregnant whales it contained 

 mucus, and in two instances in the latter class the mucus was sufficiently thick to be 

 described as a plug. 



Table XIX. Sei whale. Females. Condition of external genitalia 



Ovaries. The appearance and structure of the ovaries of the Sei whale are similar 

 to those of the Blue and Fin whales. It is practically certain that ovulation at oestrus 

 is spontaneous and does not depend upon pairing taking place. This conclusion is 

 drawn from the occurrence of non-pregnant whales with young corpora lutea in the 

 ovaries, the alternative explanation of which is that pairing is frequently unsuccessful. 

 The newly formed corpus luteum is large and easily distinguished from the older ones 

 which persist in the ovary for a very long time before they are completely resorbed, if 

 indeed they ever are. In these investigations, for convenience in reference, the corpus 

 luteum of ovulation or pregnancy, which when present is always the youngest corpus 



