METAMORPHOSIS OF AMMONITES. 57 



great number of these fossils through several strata of 

 considerable extent and thickness, and to handle hun- 

 dreds of every species as heretofore classified, must often 

 have been astonished, to see how wide is the divergence 

 in many of these species. Often he must have lost all 

 hope of ever arriving at a clear delimitation of species; 

 again and again must he have felt less inclined to dis- 

 miss the idea put forward by Darwin, ' that our species 

 are in fact only an artificial concept, a mere formula.' 

 Kayser consequently finds himself compelled to adopt 

 purely artificial limits, and speak of ' Form-series,' as 

 other writers do of Ammonites." Waagen reminds us 

 that, long before Darwin, Queenstedt had suggested the 

 Genetic connection of successive forms in geological 

 strata, and he then says : — " There are but few among 

 the Palaeontologists who have recently studied the Am- 

 monitidse under the light of the Theory of Descent, to 

 whom the facts have not brought conviction. The ex- 

 istence of Form-series, such as have been shown again 

 and again by late investigators — series in which each 

 more recent form deviates but slightly from its pre- 

 cursor, till the sum total of these small divergences re- 

 sults in a wide dissimilarity from the original species — 

 points with coercive clearness to the assumption of 

 Genetic connection." 



Zittel and Neumayr are of the same mind. Neumayr 

 writes: — "There is hardly any fact which speaks so con- 

 clusively- for the validity of the Theory of Descent as 

 the existence of Form-series, which has been proved in 

 many cases, and of which more instances will certainly 

 be found now that attention has been directed to the 

 matter. A peculiarly beautiful example is to be seen — 



