246 



CHAPTER III 



FIG. 33. The extinct Great Auk, Penguinus (Alca) im- 

 pennis L. Late- and postglacial distribution. — Solid 

 dots = on historical evidence. Open dots = subfossil 

 remains. The figured bird belongs to the Zool. Inst., 

 Lund. 



(According to Blasius, 1903, Ekman, 1922, &c.) 



(Photo Hanna Grans.) 



are extremely resistant and constitute the normal stage of dispersal of the organism. 

 The gemmulae may be carried by water but also, after drying up, by the wind; for 

 greater distances, transport with birds is usually accepted as the normal means of 

 dispersal {vide, for instance, Thienemann, 1950, p. 156). 



It was therefore suggested by some students that bird-transport from North 

 America might have been responsible for the European occurrence of Heteromeyenia 



