O EVOLUTION. 



brate) animals. It was claimed such a change could 

 only have been made by the special act of God in 

 creating a new form. 



But in the lowest fish, known as the lancelet or 

 amphioxus, we find a soft rod in place of the back- 

 bone. This is called the notochord, and represents 

 the commencement of the formation of the backbone 

 in animals. This little fish is only one or two inches 

 long, and inhabits sandy coasts. It has neither 

 limbs, heart, nor brain, and a narrow fin is the only 

 distinct fish appendage that it possesses ; but in many 

 respects it resembles the molluscs, or soft-bodied 

 invertebrates. 



One of the molluscs, the sea-squirt, or ascidian, is 

 a marine animal sh::^^ed like a bag. It attaches itself 

 to stones at low-water mark, and when handled it 

 squirts water from its orifices. Some of its species 

 are found with a permanent tail, and the first sign of 

 the notochord, the dawning backbone. 



Here in the lancelet and sea-squirt we have con- 

 necting links between the two great classes of verte- 

 brates and invertebrates, and the gap that was 

 supposed to exist has been in a measure filled. The 

 lamprey is another link above the lancelet, and other 

 forms illustrate the gradual rise of backboned 

 animals from the invertebrates. 



The articulates, or jointed animals, such as insects 

 and crustaceans (animals having a crust-like shell), 

 are allied to the molluscs by a marine worm called 



