"Shall we dare to extend the spirit of system so far as to say that it is Nature who has herself alone created this astonishing diversity of means, of contrivances, of skill, of precautions, of patience, of which the _industry_ of animals offers us so many examples? What we observe in this respect in the simple class of _insects_, is it not a thousand times more than sufficient to make us realize that the limit to the power of Nature in nowise permits her to herself produce so many marvels, but to force the most obstinate philosopher to recognize that here the will of the Supreme Author of all things has been necessary, and has alone sufficed to create so many admirable things? "Without doubt, one would be rash or, rather, wholly insensate, to pretend to assign limits to the power of the first Author of all things; but, aside from that, no one could dare to say that this infinite power could not will that which Nature even shows us it has willed"[181] (p. 67). Referring to the alleged proof of the fixity of species brought forward by Cuvier in the _Annales du Muséum d'Histoire naturelle_ (i., pp. 235 and 236) that the mummied birds, crocodiles, and other animals of Egypt present no differences from those now living, Lamarck says: "It would assuredly be very singular if it were otherwise, because the position of Egypt and its climate are still almost exactly what they were at that epoch. Moreover, the birds which live there still exist under the same circumstances as they were then, not having been obliged to change their habits. "Moreover, who does not perceive that birds, which can so easily change their situation and seek places which suit them are less subject than many other animals to the variations of local circumstances, and hence less restricted in their habits." He adds the fact that the animals in question have inhabited Egypt for two or three thousand years, and not necessarily from all time, and that this is not time enough for marked changes. He then gives the following definition of species, which is the best ever offered: "Species, then, have only a relative stability, and are invariable only temporarily." "Yet, to facilitate the study and knowledge of so many different organisms it is useful to give the name of _species_ to every similar collection of similar individuals which are perpetuated by heredity (_génération_) in the same condition, so long as the circumstances of their situation do not change enough to render variable their habits, character, and form." He then discusses fossil species in the way already described in Chapter III. (p. 75). The subject of the checks upon over-population by the smaller and weaker animals, or the struggle for existence, is thus discussed in Chapter IV.: