REMOULDING OF SPECIES. 289 



new species preserved their characteristics unchanged. Hence 

 the period during which the species persistently maintained 

 their determinate forms has been longer than the time of their 

 transformation. 



Professor Heer employs for this occurrence the expression of 

 remoulding of species*, which does not imply an insensible 

 fusion of species (for that would be opposed to the results of 

 scientific research) , nor does it trench on the privilege of geolo- 

 gists, who claim to have at their disposal tens of thousands of 

 millions of years. 



Professor Heer considers that we are still in the dark with 

 regard to the fundamental conditions of this transformation of 

 types ; and yet the transformations through which many species 

 of animals pass may give us some indications as to how we must 

 conceive of this process. It is well known that most . insects 

 only attain their perfect form after they have undergone a 

 metamorphosis. From the egg comes the caterpillar, from this 

 the pupa, and it is from the latter that the butterfly rises. The 

 caterpillar is quite different from the butterfly in the form and 

 structure of its body, as is the maggot from the fly and the 

 grub from the beetle ; and if we did not know that these earlier 

 forms of life are only young stages, we should undoubtedly 

 place them in a different class of animals. Now these earlier 

 forms of life are in many cases like the lower animals, of which 

 the young, corresponding to the larva or caterpillar, propagate 

 by division, so that a number of individuals proceed from a 

 single larva ; and these earlier animals differ from the individuals 

 which occur at the final stage of the development nearly as the 

 caterpillar differs from the butterfly; the species is therefore 

 split up into several forms, which have been produced, not by a 

 gradual transition, but by a sudden transformation. 



This process, which has been termed f( alternation of genera- 

 tions," resembles, at least in the subdivision of a species into 



* See ' La Flore Tertiaire de la Suisse,' vol. iii. p. 256, and ' Recherches 

 sur le Clirnat et la Vegetation du Pays Tertiaire,' p. 56. Professor Suess 

 (" Sur la difference et la succession de la faune Tertiaire dans les environs de 

 Vienne," Sitzungs. der Akad. in Wien, May 1863; and Professor Kolliker 

 (' Ueber die Darwin'sche Schopfungs-Theorie/ Leipzig, 18C4) have expressed 

 themselves in the same way. 



VOL. II. U 



