THE OLDEST KNOWN ANIMAL 



It is a mistake to think that evolution has meant the death or change of all the 

 life forms which were in the world in early geoloj^ic ages. Some of them have per- 

 sisted, practically unchanged, for a hundred million years or more. 



No living animal has a longer pedigree than Lingula, the shell-fish shown at 

 the left above, i)hotogra])hed natural size from a s]jccimcn taken a few years ago in 

 Manila Bay and suijjjlied by Ur. Paul Bartsch. At the right is a fossil, also natural 

 size, but with the peduncle or "tail" restored, from the Ordovician period, after 

 Billings. The Ordovician is not the lower limit of Lingula's history, however: "The 

 genus commences to be represented in the Cambrian rocks, and has continued without 

 interruption, and with no perceptible change, to the present day." 



That this genus should have survived for all these ages, and undergone practi- 

 cally no change, is striking evidence of the fact that the germ-plasm, under some 

 conditions at least, is extraordinarily constant. (Frontispiece.) 



