246 NATURAL HISTORY OF OUR SHORES 



end of the dorsal cord foreshadows the eye of the 

 vertebrates. 



It has no heart, in the proper sense, but the blood is pro- 

 pelled to the branchiae for oxidation by an arrangement 

 of the ventral muscles, while a similar arrangement on 

 the dorsal side sends the purified blood to the different 

 parts of the body. 



The young pass through developmental stages very like 

 those of some of the worms. 



The lancelet lives for the greater part of its time buried 



Fig. 104. Diagram of Amphioxns 



E. Eye. St. Stomach. 



SC. Spinal cord. AP. Atrial pore 



NC. Notochord. A. Anal opening. 



IA. Inhalant aperture. CF. Caudal fin. 



B. Branchiae. 



(About 1^ Natural size) 



just below the surface of the sand or fine shell gravel, in a 

 slanting direction, with just the tentacled orifice which 

 serves as mouth projecting above the surface. 



It swims with difficulty a few spasmodic efforts to 

 rise, and then it drops, as if exhausted, to the bottom, 

 and swiftly buries. 



It may frequently be taken at low spring tide limits in 

 the situations described, but is more usually obtained with 



