REPRODUCTION 



375 



Figure 210. Outlines of fully-developed foetuses of a Blue Whale {left), a Porpoise {centre) 



and a seal {right). The umbilicus and anus are ringed. The rigid part of the seal's body lies 



between the two stars. {Slijper, 1956.) 



the coast of Greenland that in Narwhals and Belugas the tail of the foetus 

 emerges from four to six weeks before birth, so that the foetus can practise 

 swimming against the day of its birth. Strangely enough, the same story 

 has been told in a number of scientific books and papers, not only by such 

 palaeontologists as Abel (1935), van der Vlerk and Kuenen (1956), and 

 by Ley, who calls himself a 'romantic naturalist', but also by Krumbiegel 

 (1955) in his textbook on the biology of mammals. 



But fable apart, there still remains the problem why Cetaceans do not 

 choke if, as we have said, breathing may be stimulated the moment the 

 umbilical cord ruptures or any part of the body (in their case the tail) 

 comes into contact with an environment that is colder than, or, in any 

 event, different from, the womb, while the head is still in the mother's 

 body. Actually since Cetaceans only breathe when their blowhole breaks 



