786 THE POPULAR SCIENCE MONTHLY. 



the simplification of modes of assault and defense in water and 

 air is replaced here by the most varied motions, such as creeping, 

 running, leaping, climbing, etc., by a diversity of ambushes and hid- 

 ing-places, and by the necessary adaptation of carnivora to numerous 

 modes of attack, and of herbivora to as numerous modes of escape. 



In fact, the specific variations in birds spring from their relations 

 to the surface. Hei'e, as a rule, they seek their food. Here their 

 mental powers arise. Here they develop other functions than flight, 

 other organs than wing-muscles. And it may be that the variations 

 in the fish type spring principally, in like manner, from their relations 

 to the sea-bottom, and the adaptations of carnivorous fish to the 

 powers of escape of forms thus varied. 



Thus in the process of animal evolution we reach the dwellers upon 

 the land as the most developed, and the best situated for further 

 development. Those land-animals that retreat to the other fields of 

 life retrograde in consequence. The whales have gone back in their 

 functional development until, in many points, they are affiliated with 

 the fish. The bats have sunk toward the bird-level. So the lowest in 

 function of land-animals are those which retain close affinities with 

 the air and water life of their ancestors, or have but lately migrated 

 to the land. The wingless birds are low in mind and in animal func- 

 tion. The amphibia rest at the lowest level of land-animals. The rep- 

 tiles are but a step above them. 



In the latter class, it is true, there are many which have long 

 broken loose from all connection with a water habitation. Most 

 notable among these are the serpents. But the latter, from their 

 habit of seeking safety in concealment alone, have retrograded func- 

 tionally, their limbs disappearing, and their bodies being extended 

 prone upon the earth. This location, w^hile an undoubted advantage 

 as affording concealment, is a disadvantage in development. The 

 prone condition of the serpent has caused its limbs to disappear, as 

 useless. Its ribs have taken the place of limbs, and the body has 

 extended in length sufficiently to increase the number of these imper- 

 fect limbs, and thus render them more available for motion. Its sen- 

 sory organs have necessarily become less acute from the disadvantages 

 of position. Gravitation is largely overcome, by the full support of 

 the body upon the earth. But it is replaced by a friction which is 

 equally disadvantageous. 



Thus, if we would seek the type of land-animal most likely to 

 develop functionally and mentally, we must look in an opposite direc- 

 tion to that taken by the serpent. The protection that is gained by 

 concealment is a retrograde form. The animals that advance most 

 rapidly are those that are least protected, either by powers of conceal- 

 ment, of flight, or of muscular vigor. 



For what does development mean, in its true sense, but extended 

 experience of nature ? The greater and more varied the experiences 



