142 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



and, consequently, belong to one species endowed 

 with an intense polymorphism. There are there 

 only simple forms, or, to be more precise, varieties, 

 since these Ammonites dwelt together in the same 

 locality in the Jurassic sea, and, moreover, passed 

 from one to the other by gradual transitions. 



Should we, then, accuse Fontannes of having 

 failed to notice these evident links of relationship ? 

 Assuredly not. This scrupulous palaeontologist kept 

 solely in view the making known to us and exactly 

 defining by his drawings the limits of variation of a 

 a very polymorphous type. Has he perchance gone 

 too far in this direction, and multiplied uselessly 

 imaginary species founded on subtle differences in 

 the ornamentation of the shells ? The transitions 

 between the Neumayrias of Crussol are, in fact, so 

 gradual that it is often difficult to affix a precise 

 name to the specimens collected, and every palae- 

 ontologist might, according to his personal whim, 

 either multiply further the divisions made by Fon- 

 tannes, or, on the contrary, reduce them in a large 

 proportion. 



The criticisms just formulated are not specially 

 aimed either at Bellardi or at Fontannes, but really 

 at the method generally employed in palaeontology 

 for the delimitation of species. The subject cannot 

 be exhausted in a few words. Two extreme cases 

 may present themselves. Either the palaeontologist 

 who attempts the description has at his disposal only 

 a small number of specimens of the same group, 

 gathered from one or several deposits. In this 

 case he need hardly trouble himself about tran- 

 sitions between the forms under consideration. He 



