358 



WHALES 



mammals, a number of follicles mature and protrude from the ovary 

 simultaneously, but in uniparous animals such as man, horses and cattle, 

 only one follicle generally matures at a time. 



Oddly enough, Avhales, though uniparous, have a number of protruding 

 follicles even Avhen they are not in season ; hence the resemblance of their 

 ovaries to bunches of grapes (Fig. 200). Nevertheless, only one of these 

 follicles normally matures during one season. In Blue and Fin Whales this 

 mature follicle is almost invariably fovmd in the anterior part of the ovary, 

 where the wall of that organ is thinnest. It is this follicle which sub- 

 sequently bursts (or ovulates) and which alone liberates an ovum that can 

 be fertilized and reach the uterus, there to develop into a foetus. However, 

 just like women, mares and cows, female whales, too, can give birth to 

 twins and triplets. This means that more than one follicle can mature 

 simultaneously, or that one and the same follicle can discharge a number 

 of ova. 



Once ovulation has taken place, fertilization usually ensues in most 

 animals living in their natural habitat. During gestation and lactation, 

 other follicles do not reach full maturity and are consequently somewhat 

 smaller. Some, at an earlier stage of their development, return to the 

 inside of the ovary, while others, though retaining their alveolar shape. 



Figure igg. Ovary of pregnant Fin Whale. Left: external view; right: longitudinal section. 

 CI = corpus luteurn which is pink rather than yellow ; Ca = corpus albicans; Fo :=^ follicle. 



