REPRODUCTION 



379 



Figure 213. Ventral sketch of Rorqual showing position of mammary glands. U = umbilicus; 

 M = mammary gland; j\ = nipple; A = anus. The female genital opening lies between 



the two nipple-slits. 



by difficulties, with the calf bringing up the first fish it eats, and the mother 

 massaging its belly with her snout. In the other Odontocetes which have 

 been studied, the period of lactation lasts for about one year, with the 

 exception of the porpoise and the Beluga (eight months). Right Whales 

 and Grey Whales also suckle their young for about a year, and Rorquals 

 for a shorter period, viz. Humpbacks about ten months, and Blue and Fin 

 Whales five to seven months (see the Table on pages 384-5). These 

 differences, as we have seen, may well be associated with the availability 

 of food resources. 



Whales have a shorter period of lactation than many other large 

 mammals. Thus the bison and other undomesticated 

 bovines have a period of lactation of about two years, the 

 dromedary of from eight to eighteen months, the rhinoceros 

 of fourteen months, and the elephant of as much as three 

 years. Suckling Cetacean calves rarely leave their mothers' 

 company, and, whenever the mother comes up for air, the 

 calf's blow can be seen as a small jet by the side of the 

 mother's larger one. 



By international agreement, a cow accompanied by a 

 calf may not be killed, and it is the task of the inspectors 

 aboard all factory ships to see that this clause of the 

 agi-eement is scrupulously observed, and that breaches are 

 promptly reported ; when this happens, captain and crew 

 of the catcher are deprived of their premium. Since the 

 catchers are usually miles away from the factory ships. 



Figure 214. Mammary gland of Humpback, 

 showing large ducts. {Lillie, 191 5.) 



