ii BARRANDE ON TRILOBITES 107 



specimens in every stage of growth. 

 He was good enough to drive with me 

 to the beds of rock which contained 

 them. They were the rocks forming in 

 low but steep hills the containing walls 

 of the Valley of the Moldau. They 

 consisted of a highly fissile slaty rock, 

 the planes of which were often charged 

 with the fossils. They seemed to me to 

 be singularly regular and unbroken by 

 clefts or chasms ; yet in the middle of 

 these regular and consecutive beds there 

 were members of the series which sud- 

 denly displayed new species. Barrande 

 was puzzled by the phenomenon. Where 

 could these new species come from ? It 

 never occurred to him that possibly they 

 might be born suddenly on the spot. 

 So, to meet the difficulty, he invented 

 the theory of " colonies " emigrants 

 from some other centre which had 

 migrated and settled there. Of course, 



