6o 



WHALES 



Figures 23 and 24. The beginnings of a giant. Photograph of a very young Blue Whale 

 embryo surrounded by embryonic membranes. Note the complete absence oj Jlukes. - 24. Draw- 

 ing of an 8 mm. Porpoise embryo showing rudimentary limbs. In the centre, the severed 

 umbilical cord. {Muller, ig20.) 



e.g. the Pigmy Sperm Whale and Sowerby's Whale, only the males have 

 even this vestige, to which their penis is anchored. 



But while adult whales show no external traces of hind limbs, things are 

 different with embryos. If we examine a very young embryo (20 mm. long) 

 of a whale or a dolphin, we shall in fact discover the presence of rudi- 

 mentary hind limbs. They appear as round and spatular extremities, 

 and very much resemble the hind limbs of other mammals at this stage 

 of their development. But while such extremities develop into proper 

 limbs in normal mammals, they generally disappear in Cetaceans by 

 the time the embryo has grown to about i^ inches. Of course, there are 

 exceptions, and the Russian biologist Sleotsov once came across an adult 

 dolphin with tiny pelvic fins. Such vestiges of former limbs can also be 

 distinguished on an etching by Hendrik Goltzius of a Pilot Whale stranded 

 at Zandvoort on 21st November, 1594. 



In any case, the whale's typical flukes can in no way be identified 

 with the pelvic limb. Formerly it was believed that the flukes had arisen 

 from a fusion of the hind limbs, hut a single glance at Fig. 24 is sufficient 

 to show that this belief was false and that the flukes are an outgrowth of 

 the skin and connective tissue of the tail. 



The fore-limb, though flat and fin-shaped, has survived to a far greater 



