276 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



tions,* which deserve to be called by the name of 

 explosions, it is difficult to arrive at it with exactness. 

 Some have thought them due to lesions in the em- 

 bryo or in the young individual (Blaringhem) ; 

 others to the stings of insects (A. Gautier) ; others, 

 again,, to the acts of parasitical fungi. But we 

 must admit that the search after these first causes 

 remains, as in all scientific matters, wrapt as yet 

 in deep obscurity. 



Do palaeontological observations allow us to 

 recognize in the transformations of fossil animals 

 any process of explosion similar to those so clearly 

 brought to light by modern botanists ? As already 

 said above, we cannot treat as satisfactory in so 

 grave a question any simply theoretical answer which 

 would discover in abrupt variation a more or less 

 plausible explanation of the difficulties which con- 

 front in palaeontology the exact demonstration of 

 the transformist hypothesis. It would be, indeed, 

 too convenient to say that if we do not meet in 

 terrestrial strata with any intermediate form 

 between the Gastropods and the Lamellibranchs, 

 or between the Reptiles and the Mammals, it is 

 because the first Lamellibranch or the first Mammal 

 appeared by a process of divergence so rapid that 

 there remain no traces of the intermediate links 

 necessitated by the hypothesis of a slow and con- 



* De Vries proposes to call these phenomena of abrupt change by 

 the name of mutations. This is a very regrettable expression, and 

 cannot be accepted, since Waagen, long before de Vries, gave this 

 very name to the diametrically opposite phenomenon of the slow and 

 gradual variation of fossil species, which he studied step by step and 

 from strata to strata throughout the sedimentary deposits. It is 

 preferable to give to the phenomenon observed by de Vries the name, 

 which is moreover much more expressive, of explosions, 



