EVOLUTION 1083 



of the colonel and the simian supra-orbital ridges of the pugilist. 

 A superficial trait catches the eye, and the whole face is summed up 

 in an unfair adjective. Our question here relates to great changes 

 that led from the skull of a fish to that of man. What were the most 

 important architectural movements that led from the shark's 

 humble cottage to the domed edifice of the human skull? 



There is a sense in which some backboneless animals, such as 

 wasps, have "faces"; and the old entomologists did not hesitate to 

 speak of the insect's "frons" or forehead; but if we accept Gregory's 

 definition of the face as "the food-detecting and food-trapping 

 mask in front of the brain", there is nothing to be gained by trying 

 to get further back than shark-like fishes. From these let us start. 



The shark's face has all the essentials, such as mouth, jaws, eyes, 

 nostrils, and brain-case; but it has very marked limitations, as is 

 not surprising in a structure some hundreds of millions of years 

 older than man's. A mouth — ^but turned to the under-surface of the 

 head; eyes — ^but without eyelids; nostrils — ^but not externally 

 quite shut off from the corners of the mouth; a brain-case — ^but 

 with no forehead. Moreover, the shark's brain-case is one massive 

 piece of gristle, so that it is like an old canoe dug out of a tree, 

 while man's skull is like a modern rowing-boat, built up of a large 

 number of separate pieces skilfully fitted together. In fact the 

 shark's skull corresponds merely to the gristly foundations of the 

 human skull. 



Perhaps the first great advance waS the development of bones, 

 partly in the gristly brain-box itself (the "chondrocranium"), and 

 partly plastered on to its surface from the enswathing skin and 

 membranes. Man has twenty-eight bones in his skull, and in some 

 form or other they are all to be seen in ancient fishes, now repre- 

 sented by the Mud-fishes and the Fringe-fins, which probably gave 

 rise to the first terrestrial animals, the pioneer Amphibians, whose 

 footprints are known in the late Devonian. 



Many a fish, among the extant as well as among the extinct, has 

 more skull bones than occur in man, and it must be understood that 

 one of the lines of progress has been simplification. A good example 

 may be found in the lower jaw, which has six bones on each side in 

 most reptiles, but only one in mammals. One of the notable simplifi- 

 cations was getting rid of the protective bony mask, sometimes like 

 porcelain, which covered the surface of the head in some of the 

 old-fashioned fishes. When this was got rid of there was a promiseful 

 clothing of the old surface with new muscles and with mobile skin. 

 As Gregory says: "After producing a beautiful mask-face of great 

 perfection and serviceableness. Nature started in to reduce and 

 simplify it, and eventually to cover up this mask with tender, 

 sensitive flesh." Various tjrpes have attempted mobilisation of the 

 face, but it came to little before mammals. It has been weU proved 



