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THE AMERICAN MUSEUM JOURNAL 



the baboons and the early predecessors 

 of man, have left the forests and taken 

 lip wholly new habits on the plains, so 

 that under the pressure of new condi- 

 tions of life they have changed pro- 

 foundly. But although other factors 

 may be involved in the final answer to 

 the question why have all the monkeys 

 not evolved into men, it is true that by 

 saving these relics of long past ages 

 Nature has provided us with materials 

 for elucidating the evolutionary liistory 

 of human structures. 



In considering the evolution of the 

 human face, we gain a better perspec- 

 tive by beginning with the lowest ani- 

 mals and working upward. It seems 

 that in the course of evolution the old- 

 est part of the face is the mouth. The 

 primary business of the face, in fact, is 

 to direct the mouth toward the food. 

 Some of the lowest, one-celled animals 

 show this first essential of a face, which 

 leads into a cavity that serves as a 

 stomach, and among the anemones and 

 corals and their relatives we find a well 

 develo])ed mouth, surrounded l)v sensory 

 organs (tentacles). 



The flatworms show the presence of 

 eyes in a very primitive condition, an- 

 other structure which goes to make up 

 the face of higher types; that is, there 

 is a concentration of nervous tissue sen- 

 sitive to light at one end of the animal, 

 which is shaped so as to progress in a 

 forward direction, with the beginnings 

 of a head and of a tail. In Peripafus, 

 a wormlike animal, there are little 

 tubercles on the skin equipped with 

 hooks which help to pull the food into 

 the mouth, and a number of paired 

 limblike appendages on either side be- 

 hind the mouth. These appendages 

 become of importance in insects and 

 crustaceans, those at the front end of 

 the series becoming modified into sen- 

 sory structures and also in many eases 



serving to get food and convey it to the 

 mouth. 



In some insects the tough skin which 

 covers these appendages has been modi- 

 fied into a sawlike edge, and here we 

 have a suggestion of jaws, which are 

 the next great element to be added to 

 the face. 



Finally we see in many ordinary in- 

 sects, such as a grasshopper, a rather 

 high type of face for this grade of ani- 

 mal. It is completely armored on the 

 surface with a tough skin. In many 

 lower types of vertebrates also the head 

 is armor-plated like the rest of the body 

 so that the head is protected by a hel- 

 met and the body by a cuirass. Insects 

 naturally evolved a kind of face with a 

 number of the characteristics of the 

 face of higher animals, because some 

 sort of face involving a mouth and jaws 

 and paired sense organs is necessary at 

 the front end of any animal that goes 

 after its food in a fore-and-aft direc- 

 tion. 



The very ancient fishlike vertebrates 

 of the Silurian and Devonian ages 

 also had a head covered with a bony 

 skin which formed a cuirass and a hel- 

 met, and in some {Botliriolcpi^t. etc.) 

 the eyes were on top of this helmet 

 much as they are in the grasshopper. 

 The jaw parts of this vertebrate are 

 likewise made up of bony plates on the 

 surface, and no doubt the muscles 

 pulled these jawlike plates back and 

 forth much as they do in the insects. 

 I do not mean that this fishlike animal 

 with its grasshopper-like face has been 

 evolved from the insect plan of organi- 

 zation ; I am merely suggesting that 

 general reseml)lances of this sort are 

 frequently evolved in widely ditferent 

 groups in response to similar func- 

 tional needs. 



It is not until we reach the sharks, 

 which are the most normal and typical 



