M. Senes on Glyptodon ornatus. 439 



hypothesis, the question of variation, or of the differences of 

 animals and plants, has not made a single step ; it remains 

 entire, inasmuch as there always remains to be explained the 

 first origin of form or of determination, which evidently has a 

 cause, a principle anterior to what are called media. 



As I have said elsewhere, in the numerous differences which 

 organized beings may be subject to, they never pass the limits 

 of their class to acquire the forms of a higher class : a Fish 

 will never ascend to the form of a Reptile ; the latter will never 

 attain that of a Bird, or a Bird that of a Mammal. Even in 

 monstrosities, a monster may repeat itself — it may present two 

 heads, two tails, six or eight extremities ; but it will always re- 

 main circumscribed within the limits of its class. This surpri- 

 sing phenomenon is doubtless connected with the general har- 

 mony of creation. What can be its cause ? Of this we are 

 ignorant. But it results from this, nevertheless, that everything 

 is not primitively in the materials — that evidently we must 

 conceive a principle exterior to them, which determines their 

 employment and presides in their arrangement. 



Media, however, exert a powerful influence in the production 

 and development of organized creatures. They do not create 

 the types ; but, in the physical world, they are an indispensable 

 condition of their evolution. If they created the types, only a 

 single type could exist in the same medium, there would be only 

 a single determination for the beings which would be produced 

 there. Now, on|the contrary, the same media present multitudes 

 of creatures differing in nature or in form. Moreover, if the 

 type which specializes each of these creatures were only the 

 effect, the term of action of the media, it would be in itself only 

 a simple modality, something purely passive, whilst facts show 

 evidently that, in each type, there resides an active energy, a 

 distinctly determinate organizatory pov/er. 



Specific differences therefore cannot have their cause in the 

 media in which the animals are developed, since they affect ani- 

 mals developed in the same medium, and persist immutably in 

 these same animals when transported into another medium. 

 The influence of these, being powerless to change their specific 

 organization, only introduces into it slight and superficial modi- 

 fications. Consequently, this specific organization, being fun- 

 damentally unalterable, depends on an internal cause which 

 is itself unalterable ; from^ which it follows that, both in ani- 

 mals and plants, there exist true species, not by a single type, 

 but by infinitely numerous types, which become involved and 

 linked together in proportion as the organisms, increasing in 

 perfection, become more complex. 



To prove the development of the diversity of types in the 



