THE EVOLUTION OF MAN 431 



scure, and great differences of opinion prevail. The 

 Amphioxus does indeed illustrate a prevertebrate stage, 

 but of course this animal, now living in shallow seas, 

 must be quite different in detail from our actual ances- 

 tor. We can hardly hope that fossils will be found 

 which will throw much light on this question, but the 

 patient study of existing animals may give us additional 

 clews. At all events our more or less wormlike ances- 

 tor developed a notochord, a dorsal nerve cord, and a 

 system of breathing (in water, of course) by means of 

 gill arches. In a dramatic treatment of the event, we 

 have supposed this primitive creature to say : 



We are not much to look at, but we are 



All in the way of progress. 



Our backs are stiffened by a notochord, and all above 



A slender nerve cord runs from fore to aft, 



Prophetic of a brain. This tiny spot, this little speck of black, 



Will some day be a pair of eyes, to knowingly survey the world, 



While these gill slits, ranged on each side, already serve 



To liven us with oxygen, gleaned from the waters flowing through them. 



All in the way of progress to be vertebrates, and in days to come 



Perchance, some creature with a soul. 



5. Reaching the vertebrate stage, we cannot doubt Early 

 that the first forms were fishlike, and lived in water. vei 

 The human embryo, at an early stage, shows structures 

 corresponding to the gill bars, though no longer func- 

 tioning as such. One of these ultimately becomes the 

 mandible or lower jaw. Although we thus postulate a 

 fish stage in our ancestry, we do not suppose that this 

 includes anything resembling the higher fishes of today. 

 In the modern fishes of highly specialized type, such as 

 the perch, the posterior paired fins have come to lie close 

 to or even beneath the anterior or pectoral pair; and 

 many other developments have taken place which lead 

 altogether away from the human type of structure. 



