194 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



peculiar to the Invertebrates only complicate, as a 

 matter of fact, the evidence as to the law of pro- 

 gressive growth in size. The phyletic branches are 

 here more numerous, closer together, and it seems 

 that since the remarkable attempts of Waagen, 

 Neumayr, Wurtemberger, Mojsisovics, and Hyatt, 

 palaeontologists have not made the necessary efforts 

 to reconstruct with precision the branches and 

 parallel sub-branches which represent evolution of 

 a rather entangled kind. In general there has 

 been too hasty a wish to establish the genealogical 

 relations of the great genera and families, instead 

 of following step by step the series of gradual 

 mutations of a given specific type. Certain great 

 genera, like the genus Hoplites among the Ammon- 

 ites, the genus Cerithium among the Gastropods, 

 the genus Pecten or Trigonia among the Lamelli- 

 branchs, each contain, perhaps, more than twenty 

 independent phyletic branches, which would have 

 to be solidly reconstructed before we could 

 argue on the phylogeny of the genus. Moreover, 

 among the Invertebrates the phyletic branches 

 with very slow or almost negative evolution seem 

 more frequent than with the Vertebrates. Numerous 

 genera of Foraminifera and of Radiolaria are found 

 with forms and dimensions identical from Primary 

 times up to the present epoch. I have already 

 cited facts of the same order among the Cidarides, 

 the Lingulce, the Cranice, the Nuculce, the Mytili, 

 the Acmcea, the Capuli, the Estherice, the Cypridince, 

 etc. 



Finally, and this is a last condition which must 

 not be overlooked, it is often difficult to decide if 



